A brake-pedal depression force estimation device includes: a first deceleration calculation unit which uses a vehicle-mounted wheel speed sensor to calculate a first estimated vehicle-body deceleration for the vehicle; a second deceleration calculation unit which uses a vehicle-mounted vehicle-body acceleration sensor to calculate a second estimated vehicle-body deceleration for the vehicle; a gradient acquisition unit which acquires the gradient of change for the first estimated vehicle-body deceleration; and a depression force determination unit which determines if the brake-pedal depression force applied by a driver is high or not. The gradient acquisition unit acquires a first gradient of change and a second gradient of change. The depression force determination unit is configured so as to determine the brake-pedal depression force applied by a driver to be high when the second gradient of change is equal to or exceeds the first gradient of change.