Game controller

A game controller (3) that is removably connected to a main unit (2) that has a main unit side slider (300) and is configured to execute a game process, the game controller comprising a surface front, a side surface and reverse surface, and a protruding part (314) that protrudes with respect to other parts of the reverse surface, the game controller comprising: a movable element (313) that is configured to be moved by an operation by a user, wherein the movable element is provided near the projecting part (314) on the reverse surface, the projecting part (314) is provided so as to extend beyond the movable element (313), and at least a part of the movable element (313) cannot be seen when the game controller (3) is viewed from a predetermined direction parallel to the reverse surface, a controller-side slider protruding from the side surface and is configured to slidably engage with the main unit-side slider, and a stopper member (319) configured to resist sliding movement, in one direction opposite, of the controller side slider against the main unit side slider (300), the opposite direction being a direction opposite to a direction in which the controller side slider can be inserted into the main unit side slider, in which the stop member (319) is coupled to the movable member (313 ), and the stop member moves from at least a first position to a second position in response to the movable member being operated by a user, thereby releasing a lock by the stop member (319).