A bicycle controller limits decreases in the assist force when the rotational speed of a crank changes. The bicycle controller can be mounted on a bicycle including a first transmission having at least two shift stages and configured to change a ratio of rotation of a wheel to rotation of a crank, a motor that provides assistance to human power input to the crank, and a second transmission configured to transmit a rotation force from the motor to a power transmission path extending from the crank to the wheel without changing the ratio of the rotation of the wheel to the rotation of the crank. The bicycle controller includes an electronic control unit that controls the second transmission in accordance with a condition of the bicycle and either one of a condition of the first transmission and a shift instruction to the first transmission.