<p>Disclosed is a blasting apparatus (1) for performing surface treatment on small workpieces with efficiency, e.g., to control the surface roughness thereof or to control the corner shape thereof. The blasting apparatus includes an enclosure (10b) in which a blasting chamber (10) is defined; a nozzle assembly (13) which is disposed in the blasting chamber to blast the workpieces by discharging blast particles thereto; a classifier unit (20) for separating reusable blast particles from a mixture of the blast particles discharged from the nozzle assembly and dust particles resulting from the blasting; a reservoir unit (21) for holding the blast particles to be supplied to the nozzle assembly; and a collector unit (30) for drawing in under suction and thereby collecting the remaining mixture, from which the reusable blast particles have already been separated. The blasting chamber includes at least one or more hollow tumblers (11) which are adapted to be loaded with the workpieces and disposed to be rotatable about the center axis. The tumbler has one end closed to form a bottom with the other end opened to form an opening (11d) opposite to the bottom; a plurality of through holes (11i) on the circumferential wall surface thereof; and a polygonal or circular cross section in parallel to the opening.</p>
