To provide a lubricating device for a transmission capable of improving lubricity of slide parts by supplying lubricating oil to the slide parts in the transmission from a reverse shaft.

The transmission comprises a main shaft 41 on which drive gears 51a-55a and 57a are installed, and a counter shaft 42 on which driven gears 51b-55b and 57b are installed. The main shaft 41 and the counter shaft 42 are provided in a case 10. In the revere shaft 56 provided in the case 10, an oil passage 62 is formed, and lubricating oil delivered from an oil pump is supplied to the oil passage 62 through a feed port 76. On the reverse shaft 56, an idler gear for retracting, that is a reverse idler gear 57c, is rotatably installed, and delivery ports 62a and 62b are formed in it to communicate with the oil passage 62. Lubricating oil is thus supplied from the reverse shaft 56 to the slide parts in the transmission.