A connector coupling device comprises a first connector in which a slide plate having a cam groove is provided being capable of sliding so as to traverse the first connector, a second connector having a fitting projection which is engaged with the cam groove for coupling the second connector with the first connector when the slide plate is slid toward a first direction, and which is removed from the cam groove for removing the second connector from the first connector when the slide plate is slid toward a second direction opposed to the first direction, a coupling case having a first opening into which the first connector is inserted and a second opening into which the second connector is inserted and slidablly mounted therein, and a fitting support member urging one end portion of the slide plate toward the first direction while the first connector is pushed toward the second connector inside of the case in a third direction perpendicular to the first and second directions for coupling the first connector with the second connector.