To reduce cost for installing a damping orifice.

An assembling hole 14 is drilled through a housing 1 for building a valve therein and a step part hole 15 is formed on the bottom of the assembling hole 14 so as to have the prescribed depth. Furthermore, a communication hole 11 is provided over an area from the bottom of the step part hole 15 to a damper chamber 10, and a step part 16 is formed between the communication hole 11 and the step part hole 15. Then, the step part 16 of the housing 1 is indented with a guide 22 formed to have a tooth of larger diameter than the communication hole 11 but smaller diameter than the step part hole 15 on the end peripheral surface, and to have an end center part of the same cross sectional area as a damping orifice, using an axially extended punch 20. In this case, the the part of the housing 1 forming the step part 16 is plastically deformed until coming in contact with the guide 22. Thereafter, the punch 20 is pulled out to form the damping orifice 12.