One embodiment of the present invention provides an opening/closing detection device comprising: a plurality of sensors arranged along prescribed sites of a mark attached to a vehicle; and a control unit. When the plurality of sensors that have detected a user of the vehicle perform a sequence of motions tracing the prescribed sites of the mark input detection signals having the sequence in which the prescribed sites were traced, the control unit outputs an actuation trigger signal that instructs an opening/closing body of the vehicle to actuate so as to open.