An end piece of wheel cylinder piston adjustor includes a seat section and a rock arm. One end of the rock arm is pivotally connected with the seat section via a pivot pin, whereby the rock arm is rotatable around the pivot pin. A locating body is disposed at the other end of the rock arm and extends through a guide slot. When the rock arm is swung, the locating body is driven to synchronously move within the guide slot so as to change the distance between the locating bodies connected with the end of the wheel cylinder piston. The locating bodies can be smoothly moved to facilitate the vehicle service work.