To provide a sander which is designed such that a single type of dust-proof cover can cover a main body and a disk blade made under different specifications, to thereby facilitate application of the dust-proof cover to the main body and the disk blade even if the height of the cover is different from the height in an axial direction of an output shaft of a driving source.

The sander is of a hand-held type and formed of the main body having the driving source, and a grinding device section 2 mounted on the main body. The grinding device section 2 has a mounting means 9 for detachably mounting the disk blade 8 on the output shaft 7 of the driving source, and the dust-proof cover 10 covering the disk blade 8 and the mounting means 9, and having formed therein an opening edge 10a facing a grinding object. The sander is provided with an adjusting mechanism 31 which is arranged on the periphery of the opening edge 10a of the dust-proof cover 10, and freely and automatically moves a brush 32 contacting with a grinding object along the axial direction of the output shaft 7 according to a pressing reaction produced by the grinding object.