To make return oil quickly flow into a working fluid tank when surge pressure may be generated, and to prevent occurrence of hunting when pressure difference between both end face of a spool is small, with simple structure.

The valve casing 11 of a counter balance valve 10 is provided with a working fluid chamber 30 with grease sealed therein. The working fluid chamber 30 is disposed to an end part on an oil chamber 13A side opposed to a side provided with a spring 14 for applying an urging force to the spool 12. A movable partition wall 31 is disposed to the inside of the working fluid chamber 30 to partition the chamber into chambers A, B. A throttle passage 35 connects between the chambers A, B, and rods 32a, 32b are continuously disposed to the movable partition wall 31. The rod 32a passes through a through-hole 33a formed in the casing of the working fluid chamber 30, is extended, and is connected and fixed to an end face on a side facing the oil chamber 13A of the spool 12.