To downsize a counterbalance valve and a hydraulic motor equipped with the counterbalance valve.

This counterbalance valve has a spool 30. The spool 30, set in a space S communicating to the right- and-left ports 21a, 21b distributing a working fluid, can axially reciprocate. Furthermore, the passage 37a, formed at the right side of the spool 30, delivers a part of the working fluid supplied through a right port 21a into the pressure chamber Sa of the spool 30's right side. The ball valve 38a, set in the passage 37a, blocks the back flow of the working fluid from a pressure chamber Sa to the right port 21a. The passage 37b, formed at the left side of the spool 30, delivers a part of the working fluid supplied through a left port 21b into the pressure chamber Sb of the spool 30's left side. The ball valve 38b, set in the passage 37b, blocks the back flow of the working fluid from a pressure chamber Sb to the left port 21b.