PURPOSE: To simplify a structure by composing a counterbalance valve of two divided spools so as to correspond a pair of supply/discharge passages, and moving the divided spools on the supply side of the passages so as to increase flow passage areas when the pressure in the passages gets a specified high value.

CONSTITUTION: A counterbalance valve 9 arranged between a changeover valve 1 and a running actuator 12 of a crawler vehicle is prepared by fitting divided spools 25, 26 into spool chambers 19, 19' linearly and parallelly extending inside a main body 18. Axial through-holes 52, 53 are formed on the divided spools 25, 26. Plugs 56, 57 are screwed with projections on rod bodies 54, 55 fitted to the respective through-holes. When the actuator 12 shows pumping action and pressure on a discharge side of supply/discharge passages 15, 16 gets a specified value or higher, a moving means 70 heretofore composed moves the divided spools 25, 26 on the supply side of the passages 15, 16 so as to increase flow passage areas. This movement causes relief of high-pressure fluid.