To provide a rodless rectilinear operating machine of a simple type, capable of reducing the weight and manufacturing cost and allowed to be used as an actuator of various industrial apparatus.

This rodless rectilinear operating machine 1 is provided with a screw shaft 10 supported only to be rotatably on a guide support 2, an input shaft 12 connected to one end of the screw shaft 10, a female screw body 13 screw-engaged with the screw shaft 10 to be movable only in the axial direction along the guide support 2, and a mounting bracket 15 fixed to the female screw body 13. The mounting bracket 15 is moved rectilinearly by the normal and reverse rotation of the screw shaft 10. The guide support 2 is formed by a square pipe, and one side plate 7 is provided with an axially extending guide hole 8. Tie rods 3 are disposed along the inside four corners of the guide hole, the female screw body 13 is formed like a quadrangle matching the inside of the square pipe 2. The four corners are provided with cutout parts 14 engaged with the tie rods 3, and the mounting bracket 15 is projected from the guide hole 8.