A brake hydraulic pressure generator comprising: a first brake system that communicates with at least one of a plurality of wheel brakes (FL, RR); a second brake system that communicates with the other wheel brakes (RL, FR); a master cylinder that operates in response to driver's operation of a brake operator; a first main hydraulic pressure path that is provided in the first brake system and that connects between the master cylinder and the at least one wheel brakes (FL, RR); a second main hydraulic pressure path that is provided in the second brake system and that connects between the master cylinder and the other wheel brakes (RL, FR); master cut valves (15a, 15b) that are provided in the first main hydraulic pressure path and the second main hydraulic pressure path, respectively, the master cut valves (15a, 15b) configured to open and close the first main hydraulic pressure path and the second main hydraulic pressure path, respectively; a slave cylinder that is operated by an electric actuator which is driven in accordance with an operation amount of the brake operator; and a first communication path that connects between the slave cylinder and the first main hydraulic pressure path; characterized in that: the brake hydraulic pressure generator further comprises a second communication path that connects between the slave cylinder and the second main hydraulic pressure path; wherein the slave cylinder includes a single hydraulic pressure chamber, the slave cylinder communicates with the first communication path and the second communication path through a common flow path connected to the hydraulic pressure chamber, the slave cylinder is configured to be able to increase a pressure in the first main hydraulic pressure path or the second main hydraulic pressure path on a downstream side of corresponding one of the master cut valves (15a, 15b), through the first communication path or the second communication path; and an on-off valve (16, 16a, 16b) is provided in at least one of the first communication path and the second communication path. a first brake system that communicates with at least one of a plurality of wheel brakes (FL, RR); a second brake system that communicates with the other wheel brakes (RL, FR); a master cylinder that operates in response to driver's operation of a brake operator; a first main hydraulic pressure path that is provided in the first brake system and that connects between the master cylinder and the at least one wheel brakes (FL, RR); a second main hydraulic pressure path that is provided in the second brake system and that connects between the master cylinder and the other wheel brakes (RL, FR); master cut valves (15a, 15b) that are provided in the first main hydraulic pressure path and the second main hydraulic pressure path, respectively, the master cut valves (15a, 15b) configured to open and close the first main hydraulic pressure path and the second main hydraulic pressure path, respectively; a slave cylinder that is operated by an electric actuator which is driven in accordance with an operation amount of the brake operator; and a first communication path that connects between the slave cylinder and the first main hydraulic pressure path; characterized in that: the brake hydraulic pressure generator further comprises a second communication path that connects between the slave cylinder and the second main hydraulic pressure path; wherein the slave cylinder includes a single hydraulic pressure chamber, the slave cylinder communicates with the first communication path and the second communication path through a common flow path connected to the hydraulic pressure chamber, the slave cylinder is configured to be able to increase a pressure in the first main hydraulic pressure path or the second main hydraulic pressure path on a downstream side of corresponding one of the master cut valves (15a, 15b), through the first communication path or the second communication path; and an on-off valve (16, 16a, 16b) is provided in at least one of the first communication path and the second communication path. the brake hydraulic pressure generator further comprises a second communication path that connects between the slave cylinder and the second main hydraulic pressure path; wherein the slave cylinder includes a single hydraulic pressure chamber, the slave cylinder communicates with the first communication path and the second communication path through a common flow path connected to the hydraulic pressure chamber, the slave cylinder is configured to be able to increase a pressure in the first main hydraulic pressure path or the second main hydraulic pressure path on a downstream side of corresponding one of the master cut valves (15a, 15b), through the first communication path or the second communication path; and an on-off valve (16, 16a, 16b) is provided in at least one of the first communication path and the second communication path.