This electric booster device is provided with a brake actuator and a brake actuator control device. The brake actuator outputs, as pressing force, input based on operation of a brake operation member, the output assisted by drive from a motor 96. The control device is provided with an operation displacement acquisition unit 11 that acquires an operation displacement quantity Sp based on the operation of the brake operation member. The control device is provided with a target rotational angle calculation unit 12 that calculates a target rotational angle Mt. The control device is provided with an assist mechanism control unit 13 that causes the motor 96 to drive on the basis of the target rotational angle Mt. The target rotational angle calculation unit 12 calculates the target rotational angle Mt so that the relationship between the operation displacement quantity Sp and the pressing force when the operation displacement quantity Sp is increasing and the relationship between the operation displacement quantity Sp and the pressing force when the operation displacement quantity Sp is decreasing differ from one another.