Yes, all chocolate has caffeine in it. The amount of caffeine present can vary. The amount of caffeine in chocolate is heavily dependent on the varieties of cacao used to make it as well as how dark the chocolate was roasted during the chocolate's manufacture. There is also another alkaloid called theobromine in cocoa which is similar in structure to caffeine.
There is more caffeine in forestero cocoa (which is the bulk of the world's cocoa and has its roots in the upper Amazon basin) than there is criollo cocoa (which is the fine flavored cocoa with genetics from Venezuela). Conversely, criollo cacao has larger amounts of theobromine than it does caffeine.
Current research in cocoa uses mass spectroscopy to analyze the ratio of theobromine to caffeine to determine the genetic heritage of various cocoas. This research has proved useful during archaeological studies of ancient pots (with remains of the ancient cocoa drinks) to determine the varieties of cocoa used during the time of the Aztecs and Mayas.
It should be pointed out that there is an internet rumor that chocolate has no caffeine in it. This is incorrect.