A hydraulic pressure generating device includes a base body having a master cylinder configured to generate a brake hydraulic pressure and a slave cylinder configured to generate a brake hydraulic pressure. The base body is provided with a motor configured as a driving source for the slave cylinder and a control device configured to control the motor. A motor shaft of the motor, a cylinder axis of the master cylinder, and a cylinder axis of the slave cylinder are disposed in parallel with each other. Then a virtual plane including the cylinder axis of the master cylinder is set as a reference plane, a housing of the control device is disposed on one side of the reference plane and the motor is disposed on the other side of the reference plane.