The invention relates to the field of well drilling, in particular, to downhole hydraulic motors. The objective of the invention is to improve energy characteristics and reliability of operation of a volumetric downhole motor. The technical result is elimination of contact friction, an increase in the starting torque value of the volumetric downhole motor and an increase in the body torque for well drilling. The technical result is achieved by the volumetric downhole motor comprising a body consisting of an upper half and a lower half connected by a detachable rigid joint, a circular cavity with a bottom, and semi-cylindrical blades, wherein, in accordance with the invention, the upper and lower body halves have coaxial central channels, the upper body half is composed of cylinders inserted inside each other, connected by the semi-cylindrical blades and forming an annular cavity communicating with the central channel via openings between the upper half of the inner cylinder and semi-cylindrical blades, and wherein the surface of the central channel below the openings has polarly transverse steps in the direction of the body rotation, grooves running from the central channel on the body bottom part pass in the form of a spiral relative to the body center line over the periphery and leave the body bottom part in the direction opposite to that of the body rotation.
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