In a helical compressor, a helical compression unit is accommodated in the case. The compression unit has a cylinder, a roller eccentrically disposed in the cylinder and a helical blade disposed between an inner surface of the cylinder and the roller for separately forming a plurality of compression chambers therebetween along an axial direction of the roller. A motor unit is accommodated in the case and is operatively connected to the helical compression unit through a rotating shaft for eccentrically rotating the roller in the cylinder through the rotating shaft. According to the rotation of the roller, compressive fluid sucked into a lower compression chamber is moved along an axial direction of the rotating shaft while being sequentially compressed. The helical compression unit and the motor unit is arranged so that the helical compression unit and the motor unit are partially overlapped to each other along the axial direction.