A stabilizer device, comprising: a stabilizer bar having both ends connected to a pair of wheel holding portions (18R, 18L) each of which holds a corresponding one of right and left wheels (10FR, 10FL) and moves with the corresponding wheel in a vertical direction relative to a vehicle body; a pair of cylinders each containing hydraulic fluid and disposed between the vehicle body and a corresponding one of a pair of right and left supported portions (16sR, 16sL) of the stabilizer bar such that the pair of supported portions (16sR, 16sL) are supported by the vehicle body, each of the cylinders being configured to be extended and retracted as a corresponding one of the right and left wheels (10FR, 10FL) rebounds and bounds with respect to the vehicle body, and each of the cylinders including a first liquid chamber having a capacity that increases when a corresponding one of the right and left wheels (10FR, 10FL) rebounds and that decreases when the corresponding wheel bounds and a second liquid chamber having a capacity that decreases when the corresponding wheel rebounds and that increases when the corresponding wheel bounds; a first communication passage configured to allow first liquid chamber of a first cylinder of the pair of cylinders and second liquid chamber of a second cylinder of the pair of cylinders to communicate with each other; a second communication passage configured to allow second liquid chamber of the first cylinder and first liquid chamber of the second cylinder to communicate with each other; an inter-passage communication passage configured to allow the first communication passage and the second communication passage to communicate with each other; an on-off valve disposed in the inter-passage communication passage and switched between an open state and a closed state to open and close the inter-passage communication passage; and a controller configured to control operation of the on-off valve to selectively attain an inter-passage communicating state in which the first communication passage and the second communication passage communicate with each other and an inter-passage non-communicating state in which the first communication passage and the second communication passage do not communicate with each other, characterized in that: the stabilizer device includes a holder with which the stabilizer bar is held at a held portion by the vehicle body while allowing the stabilizer bar to rotate as one of the right and left wheels (10FR, 10FL) bounds and the other wheel rebounds, the held portion being located in a middle part of the stabilizer bar in a vehicle-width direction of a vehicle. a stabilizer bar having both ends connected to a pair of wheel holding portions (18R, 18L) each of which holds a corresponding one of right and left wheels (10FR, 10FL) and moves with the corresponding wheel in a vertical direction relative to a vehicle body; a pair of cylinders each containing hydraulic fluid and disposed between the vehicle body and a corresponding one of a pair of right and left supported portions (16sR, 16sL) of the stabilizer bar such that the pair of supported portions (16sR, 16sL) are supported by the vehicle body, each of the cylinders being configured to be extended and retracted as a corresponding one of the right and left wheels (10FR, 10FL) rebounds and bounds with respect to the vehicle body, and each of the cylinders including a first liquid chamber having a capacity that increases when a corresponding one of the right and left wheels (10FR, 10FL) rebounds and that decreases when the corresponding wheel bounds and a second liquid chamber having a capacity that decreases when the corresponding wheel rebounds and that increases when the corresponding wheel bounds; a first communication passage configured to allow first liquid chamber of a first cylinder of the pair of cylinders and second liquid chamber of a second cylinder of the pair of cylinders to communicate with each other; a second communication passage configured to allow second liquid chamber of the first cylinder and first liquid chamber of the second cylinder to communicate with each other; an inter-passage communication passage configured to allow the first communication passage and the second communication passage to communicate with each other; an on-off valve disposed in the inter-passage communication passage and switched between an open state and a closed state to open and close the inter-passage communication passage; and a controller configured to control operation of the on-off valve to selectively attain an inter-passage communicating state in which the first communication passage and the second communication passage communicate with each other and an inter-passage non-communicating state in which the first communication passage and the second communication passage do not communicate with each other, characterized in that: the stabilizer device includes a holder with which the stabilizer bar is held at a held portion by the vehicle body while allowing the stabilizer bar to rotate as one of the right and left wheels (10FR, 10FL) bounds and the other wheel rebounds, the held portion being located in a middle part of the stabilizer bar in a vehicle-width direction of a vehicle.