Abstract: A game controller includes a casing, a control circuit module received in the casing, a plurality of controlling units embodying as a left control stick, a direction key, a function key, and a right control stick respectively, wherein at least two of the controlling units form as two interchangeable controlling units respectively which are detachable from the casing. A plurality of terminal seats are spacedly provided on the casing for detachably retaining the interchangeable controlling units in position, wherein the number of the terminal seats are corresponding to the number of the interchangeable controlling units to be interchangeably mounted at the casing. The interchangeable controlling units are detachably coupled at the terminal seats to electrically connect to the control circuit module. The positions of the interchangeable controlling units are interchanged according to the game setting and players' habits.