A brake system for a vehicle, comprising an electric brake actuator and a master cylinder, said electric brake actuator being communicated and connected with said master cylinder, said master cylinder being configured to generate a master cylinder pressure according to a braking operation by a driver, and generate a brake hydraulic pressure, based on an electric signal according to the braking operation, the electric brake actuator comprising: a cylinder provided with a piston (88a, 88b) that is displaced along a hydraulic pressure chamber (98a, 98b): an electric motor configured to drive the piston (88a, 88b); and an actuator housing formed separable from the cylinder and from the electric motor, wherein the actuator housing houses a gear mechanism configured to transmit a rotational driving force of the electric motor, and a conversion mechanism configured to convert the rotational driving force transmitted through the gear mechanism, into a linear movement and transmit the linear movement to the piston (88a, 88b), characterized in that the actuator housing includes a mount portion configured to be mounted to allow the electric brake actuator to be supported, wherein the mount portion comprises: a first boss portion and a second boss portion protruding toward left and right sides in a direction substantially perpendicular to an axial line of the cylinder; and a third boss portion protruding downward from the cylinder. the electric brake actuator comprising: a cylinder provided with a piston (88a, 88b) that is displaced along a hydraulic pressure chamber (98a, 98b): an electric motor configured to drive the piston (88a, 88b); and an actuator housing formed separable from the cylinder and from the electric motor, wherein the actuator housing houses a gear mechanism configured to transmit a rotational driving force of the electric motor, and a conversion mechanism configured to convert the rotational driving force transmitted through the gear mechanism, into a linear movement and transmit the linear movement to the piston (88a, 88b), a cylinder provided with a piston (88a, 88b) that is displaced along a hydraulic pressure chamber (98a, 98b): an electric motor configured to drive the piston (88a, 88b); and an actuator housing formed separable from the cylinder and from the electric motor, wherein the actuator housing houses a gear mechanism configured to transmit a rotational driving force of the electric motor, and a conversion mechanism configured to convert the rotational driving force transmitted through the gear mechanism, into a linear movement and transmit the linear movement to the piston (88a, 88b), the actuator housing includes a mount portion configured to be mounted to allow the electric brake actuator to be supported, wherein the mount portion comprises: a first boss portion and a second boss portion protruding toward left and right sides in a direction substantially perpendicular to an axial line of the cylinder; and a third boss portion protruding downward from the cylinder. a first boss portion and a second boss portion protruding toward left and right sides in a direction substantially perpendicular to an axial line of the cylinder; and a third boss portion protruding downward from the cylinder.