Stabilizer device and stabilizer system

In a stabilizer device, a stabilizer bar having both ends connected to right and left wheel holding portions is supported at a pair of right and left supported portions of the stabilizer bar by a vehicle body via a pair of cylinders that can be extended and retracted based on vertical movement of wheels. The stabilizer device includes two communication passages, each of which allows one of two liquid chambers of one of the pair of cylinders and the other of two liquid chambers of the other cylinder to communicate with each other. The stabilizer device further includes an inter-passage communication passage that allows the two communication passages to communicate with each other, and an on-off valve that is opened and closed to open and close the inter-passage communication passage.