To make capacity of a pump smaller while coping with various kinds of driving.

A brake gear is provided with: a brake booster which increases force added to a brake pedal by a negative pressure which is a pressure lower than atmospheric pressure; a pump which generates the negative pressure; and control means for controlling drive of the pump. The control means determines whether or not a frequency of operations added to the brake pedal is more than a first predetermined threshold, when it is determined that the frequency of operations added to the brake pedal is more than the first threshold, determines whether or not the negative pressure is higher than a second predetermined threshold, when it is determined that the negative pressure is higher than the second threshold, drives the pump at high speed, when the pump is driven at high speed, determines whether or not the negative pressure is higher than a third predetermined threshold, and when it is determined that the negative pressure is higher than the third threshold, drives the pump at low speed.