Why does the devil exist?

Answer 1

Because he misbehaved in heaven.

Another answer:

The biblical evidence is that Lucifer (later called Satan) was standing on the earth when he made his decision to attack God in heaven:

"For thou hast said in thine heart, I will ascend into heaven, I will exalt my throne above the stars of God... I will ascend above the heights of the clouds; I will be like the Most High." (Isa.14:13-14).

"Clouds" are a phenomenon that occurs within the earth's breathable atmosphere. Lucifer was standing on the earth when he formulated his plan to attack God in heaven.

God merely cast him back down onto the earth where he originated... and confined he and his angels here.

"...God spared not the angels that sinned, but cast them down to hell [tartarus; a spiritual condition of restraint], and delivered them into chains of darkness, to be reserved unto Judgment..." (II Peter 2:4).

"...the angels which kept not their first estate... He hath reserved in everlasting chains under darkness unto the Judgment of the Great Day." (Jude 1:6)

As the scriptures state... their present "confinement" is pending the Day of Judgment. In other words: they are waiting for their "court case" to come up on the docket.

Which will be right after God's saints are appointed by Christ to rule over the earth.

"...the Ancient of Days came [Jesus Christ], and Judgment was given to the saints of the Most High; and the time came that the saints possessed the Kingdom." (Dan.7:22)

"Do ye not know that the saints shall Judge the world?... Know ye not that we shall judge angels?" (I Cor.6:2-3)

Satan and his angels' confinement to earth is a temporary measure, pending the conclusion of God's plan and His appointment of Judges to try them for their crimes.

In the meantime... they have been teaching man all about evil, iniquity, wickedness, lawlessness, hatred, lust, envy, jealousy, greed... and the fruits thereof. It serves as a part of man's "character development," that in the end God's Children:

"... may know to refuse the evil, and choose the good." (Isa.7:15)

"I call heaven and earth to record this day against you, that I have set before you life and death, blessing and cursing: therefore choose life, that both you and your seed may live: that thou mayest love the Lord thy God, and that thou mayest obey His voice, and that thou mayest cleave unto Him: for He is thy Life, and the length of thy days..." (Deut.30:19-20).

Answer 2

Well, God Almighty has not put the devil in hell yet. God kicked Lucifer out of heaven when Lucifer started to believe he was God. And he sinned, so God kicked him out of heaven. Since then, Satan preyed on people and lives to make people turn away from God by making them sin and mess their lives up. At the end of time, after the rapture and the tribulation (darkest era the world will ever see-ask your pastor) :) God will judge everyone depending on how they acted and what they did for God. If you were not a Christian, you would go to hell with the devil, Antichrist (devil's creation to turn people against God) and the false prophet (Antichrist's helper). Yeah, for eternity. Not fun. Hope my answer helped!

Answer 3

The devil used to be an angel.O:)