PURPOSE: To provide a camless opening device requiring an electric-powered means such as a pulse motor, a servo motor, etc., as a driving source, directly displacing wire rope length by the electric-powered means to carry out opening movement.

CONSTITUTION: In a negative type opening device for providing opening movement by tension and relaxation of wire ropes 4 and 5, etc., connected to heald frames 10 and 10' suspended from spring members 2 and 3, the opening device is provided with a driving part 1 for electric-powered means M1, M2, M3... so as to displace route length of the right and the left wire ropes 4 and 5, etc., connected to the heald frames 10 and 10' at a part of an arbitrary place of the route length, the electric-powered means are synchronized with the revolution of a main shaft and opening movement of each heald frame is carried out to provide the objective opening device 100 for a weaving machine L.