A control device includes an electronic controller configured to control a transmission to shift a transmission ratio of a human-powered vehicle in accordance with a first shifting condition set based on a first reference value. The electronic controller is configured to control the transmission to restrict shifting of the transmission ratio of the human-powered vehicle regardless of the first shifting condition upon determining a second shifting condition set based on a second reference value is satisfied. The second reference value includes at least one of a reference value indicating an acceleration tendency of the human-powered vehicle and a reference value indicating a deceleration tendency of the human-powered vehicle.