A compact orifice and an orifice clogging preventing mechanism respectively integrated with a hydraulic control unit in the orifice of a fluid passage of the hydraulic control unit formed by inserting plate between two parts and the orifice clogging preventing mechanism. One groove type fluid passage formed in the first part is in communicate with a groove type fluid passage formed in the second part via a group of small holes formed in a plate. The groove type fluid passage in the second part is in communicate with a separate groove type fluid passage in the first part from the groove type fluid passage in the first part via an orifice formed on the plate and the diameter of each small hole in the group of small holes is set to a smaller value than that of the orifice.