A leaning posture control device for a left-right-inclined-wheel-equipped leaning vehicle, the leaning posture control device being configured to control a leaning posture of the leaning vehicle, and the leaning vehicle including: a lean body frame configured to lean leftward when the vehicle is turning leftward in a left-right direction of the vehicle, and to lean rightward when the vehicle is turning rightward in the left-right direction of the vehicle; a right inclined wheel supported on the lean body frame, the right inclined wheel being leaned leftward when the vehicle is turning leftward in the left-right direction of the vehicle and being leaned rightward when the vehicle is turning rightward in the left-right direction of the vehicle; a left inclined wheel supported on the lean body frame and disposed at a side of the right inclined wheel in the left-right direction of the vehicle, the left inclined wheel being leaned leftward when the vehicle is turning leftward in the left-right direction of the vehicle and being leaned rightward when the vehicle is turning rightward in the left-right direction of the vehicle; and another inclined wheel supported on the lean body frame and disposed ahead of or behind the right inclined wheel and the left inclined wheel in a front-rear direction of the vehicle, the another inclined wheel being leaned leftward when the vehicle is turning leftward in the left-right direction of the vehicle and being leaned rightward when the vehicle is turning rightward in the left-right direction of the vehicle, characterized in that the leaning posture control device is configured to control a torque of at least one of the right inclined wheel or the left inclined wheel arranged in the left-right direction of the vehicle so as to suppress a change in a lean of the lean body frame in a left direction of the vehicle while the lean body frame is leaned in the left direction or a change in a lean of the lean body frame in a right direction of the vehicle while the lean body frame is leaned in the right direction, based on a physical quantity concerning side-slip, in the left direction of the vehicle or in the right direction of the vehicle, of the right inclined wheel, the left inclined wheel, and the another inclined wheel disposed ahead of or behind the right inclined wheel and the left inclined wheel in the front-rear direction of the vehicle. a lean body frame configured to lean leftward when the vehicle is turning leftward in a left-right direction of the vehicle, and to lean rightward when the vehicle is turning rightward in the left-right direction of the vehicle; a right inclined wheel supported on the lean body frame, the right inclined wheel being leaned leftward when the vehicle is turning leftward in the left-right direction of the vehicle and being leaned rightward when the vehicle is turning rightward in the left-right direction of the vehicle; a left inclined wheel supported on the lean body frame and disposed at a side of the right inclined wheel in the left-right direction of the vehicle, the left inclined wheel being leaned leftward when the vehicle is turning leftward in the left-right direction of the vehicle and being leaned rightward when the vehicle is turning rightward in the left-right direction of the vehicle; and another inclined wheel supported on the lean body frame and disposed ahead of or behind the right inclined wheel and the left inclined wheel in a front-rear direction of the vehicle, the another inclined wheel being leaned leftward when the vehicle is turning leftward in the left-right direction of the vehicle and being leaned rightward when the vehicle is turning rightward in the left-right direction of the vehicle, characterized in that the leaning posture control device is configured to control a torque of at least one of the right inclined wheel or the left inclined wheel arranged in the left-right direction of the vehicle so as to suppress a change in a lean of the lean body frame in a left direction of the vehicle while the lean body frame is leaned in the left direction or a change in a lean of the lean body frame in a right direction of the vehicle while the lean body frame is leaned in the right direction, based on a physical quantity concerning side-slip, in the left direction of the vehicle or in the right direction of the vehicle, of the right inclined wheel, the left inclined wheel, and the another inclined wheel disposed ahead of or behind the right inclined wheel and the left inclined wheel in the front-rear direction of the vehicle.