burned tower
You must trade Magmar while holding the Magmarizer
If you breed magmar and ditto, you will get and egg that will hatch into magby.
u need to treade it with a magmarizer
If you have a magmar with you on your team that will help.
in soul silver, you can get magmar in the burned tower. then i guess you can just evolve it
You can use a cheat. Otherwise, there is no way.
in a volcanoe
You catch magmar at the burned tower at Eaurtek city.
Magmar > trade w/ Electrizer > Magmortar
Try to get these Pokemon :Magmar Pidgeot and any electric Pokemon with a good move like charge beam feraligatr also helps.
To obtain a Magby in Pokemon Soul Silver you first have to capture a Magmar and bread him with a captured Ditto. You have to breed these two Pokemon at the daycare center.