A gear shift controller includes a detection circuit and a control unit. The detection circuit is configured to determine traveling state information about a traveling state of a human-powered vehicle. The control unit is configured to receive the traveling state information from the detection circuit to control a shift standby time of a transmission of the human-powered vehicle. The traveling state information includes information other than traveling speed information about a traveling speed of the human-powered vehicle and crank information about crank rotation information of the human-powered vehicle.