To provide a surface treatment device of cylindrical or columnar works making use of the flow of magnetic abrasive grains stored in a treatment tank which is improved so that the magnetic abrasive grains is prevented from flowing out of the treatment tank while the surface treatment device is in service, and the surface treatment is uniformly achieved.

This surface treatment device comprises a non-magnetic treatment tank 2 with the magnetic abrasive grains 1 stored therein and rotational magnetic field generating devices 3a and 3b to apply the rotational magnetic field to the treatment tank, the treatment tank 2 comprises a cylindrical body 2a a closed wall 2b on one end side thereof and an elastic wall 2c on the other end side thereof, the works A are freely taken in or taken out of the elastic wall 2c, and holders 5 which are engaged with the other end parts of the works A and integratedly rotated with the works are closely and slidably attached to the elastic wall.