A vehicle brake hydraulic pressure control device comprising: a split road deciding unit configured to decide whether or not a road in contact of wheels of a vehicle is a split road; a hydraulic pressure controlling unit capable of executing a limiting processing for limiting a hydraulic pressure of a wheel brake on a high-μ road side so that a differential pressure between a hydraulic pressure of a wheel brake on a low-μ road side and the hydraulic pressure of the wheel brake on the high-μ road side becomes equal to or smaller than an acceptable differential pressure, under condition that the split road deciding unit decides that the road is the split road; and a vehicle state deciding unit configured to decide whether or not the vehicle is in an unstable state, wherein the hydraulic pressure controlling unit is capable of executing: a first control for determining the acceptable differential pressure in accordance with a first method during a predetermined time period after the split road deciding unit decides that the road is the split road; a second control for determining the acceptable differential pressure in accordance with a second method after the predetermined time period passes; and a third control configured to be started under condition that during the second control, an anti-lock brake control on the wheel brake on the high-μ road side is started, the acceptable differential pressure is equal to or larger than a first threshold, or a steering angle of a steering is equal to or larger than a second threshold, and wherein during the third control, the hydraulic pressure controlling unit is configured to decrease the hydraulic pressure of the wheel brake on the high-μ road side if the vehicle state deciding unit decides that the vehicle is in an unstable state, characterized in that the hydraulic pressure controlling unit is configured to set an upper limit of the hydraulic pressure of the wheel brake on the high-μ road side so that the upper limit has a value larger than a value obtained by adding the acceptable differential pressure to the hydraulic pressure of the wheel brake on the low-μ road side, if during the third control, the vehicle state deciding unit decides that the vehicle is not in an unstable state, and also to determine the upper limit based on a deviation between the actual yaw rate of the vehicle and a target yaw rate, if during the third control, the vehicle state deciding unit decides that the vehicle is in an unstable state. a split road deciding unit configured to decide whether or not a road in contact of wheels of a vehicle is a split road; a hydraulic pressure controlling unit capable of executing a limiting processing for limiting a hydraulic pressure of a wheel brake on a high-μ road side so that a differential pressure between a hydraulic pressure of a wheel brake on a low-μ road side and the hydraulic pressure of the wheel brake on the high-μ road side becomes equal to or smaller than an acceptable differential pressure, under condition that the split road deciding unit decides that the road is the split road; and a vehicle state deciding unit configured to decide whether or not the vehicle is in an unstable state, wherein the hydraulic pressure controlling unit is capable of executing: a first control for determining the acceptable differential pressure in accordance with a first method during a predetermined time period after the split road deciding unit decides that the road is the split road; a second control for determining the acceptable differential pressure in accordance with a second method after the predetermined time period passes; and a third control configured to be started under condition that during the second control, an anti-lock brake control on the wheel brake on the high-μ road side is started, the acceptable differential pressure is equal to or larger than a first threshold, or a steering angle of a steering is equal to or larger than a second threshold, and wherein during the third control, the hydraulic pressure controlling unit is configured to decrease the hydraulic pressure of the wheel brake on the high-μ road side if the vehicle state deciding unit decides that the vehicle is in an unstable state, a first control for determining the acceptable differential pressure in accordance with a first method during a predetermined time period after the split road deciding unit decides that the road is the split road; a second control for determining the acceptable differential pressure in accordance with a second method after the predetermined time period passes; and a third control configured to be started under condition that during the second control, an anti-lock brake control on the wheel brake on the high-μ road side is started, the acceptable differential pressure is equal to or larger than a first threshold, or a steering angle of a steering is equal to or larger than a second threshold, and wherein during the third control, the hydraulic pressure controlling unit is configured to decrease the hydraulic pressure of the wheel brake on the high-μ road side if the vehicle state deciding unit decides that the vehicle is in an unstable state,