Abstract: A braking device for a vehicle is provided which includes a hydraulic booster to make wheels of the vehicle produce frictional braking force, a solenoid valve installed in a flow path connecting between a brake fluid accumulator and a servo chamber of the hydraulic booster, and a collision avoidance controller. When determining that there is a risk of a collision with an obstacle, the collision avoidance controller opens the first solenoid valve to achieve emergency braking to minimize the risk of the collision. Basically, the emergency braking is achieved only using the solenoid valve, thus allowing an emergency avoidance mechanism of the braking device to be constructed with a minimum of equipment and facilitating the mountability of the braking device in vehicles.