An adjustable device suitable for ultra-precision turning machining comprises a cutter and a base. A vertical dovetail groove guide rail is formed in the middle of the front side of the base in the mode that the direction of a cutter head of the cutter serves as the forward direction. A dovetail sliding block is assembled in the dovetail groove guide rail in a sliding mode. Vertical locking assemblies are arranged on the portions, located on the left side and the right side of the front portion of the dovetail groove guide rail, of the base. The upper portion of the dovetail sliding block stretches out of the upper surface of the base. A lifting power mechanism which adjusts the height of the dovetail sliding block is arranged on the rear portion of the base. A fixed-angle rotation adjusting mechanism is connected with the lower half portion of the front end face of the dovetail sliding block, and the cutter handle end of the cutter is installed on the fixed-angle rotation adjusting mechanism. By the adoption of the adjustable device suitable for ultra-precision turning machining, the height and the angle of the cutter can be adjusted according to the machining requirement, operation is easy, the precision is high, and the turning machining efficiency is improved.