A terminal attaching/detaching device includes a housing, an engaging member, and a movable member. The engaging member is configured to move in a first direction toward a terminal inserted in the housing to engage with the terminal, and is configured to move from the terminal inserted in the housing in a second direction to disengage from the terminal. The movable member is configured to move in concert with the engaging member in the moving process thereof in the first direction, and is configured to move the engaging member from the terminal inserted in the housing in the second direction, so that the engaging member is disengaged from the terminal.