A computer storing an operating system therein and including a first case, a second case, a driving mechanism and a starting unit is provided. The driving mechanism is connected between the first case and the second case. The starting unit is disposed at the first case, electrically connected to the driving mechanism, and used to start the operating system. When the starting unit starts the operating system, the driving mechanism drives a relative movement between the first case and the second case to enhance heat dissipation efficiency of the computer.