To provide a blast device having excellent practicality obtained by improving durability, working accuracy and cost performance.

A work piece 5 is rotatably held by a holding means 12. The work piece 5 is rotated by rotary drive means 17 through the medium of the holding means 12. A jet nozzle 23 is oppositely disposed to the worked surface of the work piece 5. Relative position change means 25 and 26 change a relative positions of the work piece 5 and the jet nozzle 23 with the lapse of time when jetting abrasive grain from the jet nozzle 23. The tip of the jet nozzle 23 is covered by a chamber 31. Dust occurring inside the chamber 31 is collected by a dust collector 41. As a result, a groove 6 having a desired pattern is formed on the worked surface of the work piece 5.