A wheel cylinder adjuster includes a body, a push rod, a resilient member and a positioning member. The push rod extends through the body and the resilient member is mounted to the push rod and located in the body. The push rod has a positioning part connected thereto and the positioning part contacts one end of the resilient member. The push rod has a connector and an activating disc respectively connected to two ends thereof, the connector has a holding rod extending therethrough. The positioning member is connected to the push rod so that the left-sided wheel cylinder and the right-sided wheel cylinder can be adjusted by using the single wheel cylinder adjuster.