To provide a device capable of reducing the temperature difference between a knitting member side and its opposite side in a machine space for preventing a phenomenon of making guiding needles in contact with knitting needles on restarting a warp knitting machine after stopping for a long period of time.

This thermal distortion-preventing device is constituted by installing an oil-circulating means so as to circulate a lubricating oil and an injection nozzle 2 joined with the oil-circulating means in a warp knitting machine installed with an oil heater 9 in the lubricating oil 5 stored at the inside of the machine space 1, for spraying the lubricating oil to the inside surface of the machine space so as to reduce the temperature difference between the knitting member side and its opposite side of the machine space and make the temperature difference between the knitting member side and its opposite side of the machine space as a constant throughout the times of the working and stopping of the knitting machine. Thereby, a distortion of the machine space is prevented and a phenomenon of making guiding needles in contact with knitting needles on restarting the knitting machine after stopping the machine for a long period of time, is also prevented.