A washing device of a substrate for a magnetic recording medium of the present invention includes an immersion tank; a plurality of screw conveyors that are provided in the immersion tank and that hold the substrates for a magnetic recording medium; and a rotation mechanism that causes synchronous rotation of and supports the plurality of screw conveyors, wherein both ends of main shafts of the screw conveyors are provided outside of the immersion tank, the main shafts of these screw conveyors penetrate the tank walls of the immersion tank in a non-contact manner, and the plurality of substrates for a magnetic recording medium that are held by the plurality of screw conveyors are washed by a wet process using a washing liquid that is contained in the immersion tank.