A shot-blasting apparatus comprising: a cabinet; a plurality of process chambers (13a, 13b) provided inside the cabinet in such a manner that each of the process chambers (13a, 13b) is capable of housing a workpiece therein and selectively movable between a carry-in-and-out position and a projection position; air inlet ports for introducing external air into the process chambers (13a, 13b) therethrough; and an air outlet port provided at a position opposed to the air inlet port across process chamber (13a, 13b) set at the projection position, and linearly communicated with an internal space of the process chamber (13a, 13b) set at the projection position, wherein, according to suction from the air outlet port, air is caused to flow from the air inlet port into the process chamber (13a, 13b) set at the projection position, and led to the air outlet port while passing through the process chamber (13a, 13b) set at the projection position, the shot-blasting apparatus further comprising an approximately cylindrical-shaped rotary hanger having a top plate, a bottom plate, and a partition plate (12a, 12b) connecting the top plate and the bottom plate together to form the process chambers (13a, 13b), the rotary hanger being rotatably disposed within the cabinet, wherein the process chambers (13a, 13b) are spaced apart from each other in a circumferential direction of the rotary hanger, wherein the process chambers (13a, 13b) are provided at intervals of a given angle, characterised in that the shot-blasting apparatus further comprises external air introduction chambers (17, 18), each one being provided adjacent to a respective the process chamber (13a, 13b), wherein each external air introduction chamber (17, 18) is partitioned with respect to the process chambers (13a, 13b) by the partition plate (12a, 12b), and has an external air introduction port communicated with the air inlet port and the air outlet port. a cabinet; a plurality of process chambers (13a, 13b) provided inside the cabinet in such a manner that each of the process chambers (13a, 13b) is capable of housing a workpiece therein and selectively movable between a carry-in-and-out position and a projection position; air inlet ports for introducing external air into the process chambers (13a, 13b) therethrough; and an air outlet port provided at a position opposed to the air inlet port across process chamber (13a, 13b) set at the projection position, and linearly communicated with an internal space of the process chamber (13a, 13b) set at the projection position, wherein, according to suction from the air outlet port, air is caused to flow from the air inlet port into the process chamber (13a, 13b) set at the projection position, and led to the air outlet port while passing through the process chamber (13a, 13b) set at the projection position, the shot-blasting apparatus further comprising an approximately cylindrical-shaped rotary hanger having a top plate, a bottom plate, and a partition plate (12a, 12b) connecting the top plate and the bottom plate together to form the process chambers (13a, 13b), the rotary hanger being rotatably disposed within the cabinet, wherein the process chambers (13a, 13b) are spaced apart from each other in a circumferential direction of the rotary hanger, wherein the process chambers (13a, 13b) are provided at intervals of a given angle, characterised in that the shot-blasting apparatus further comprises external air introduction chambers (17, 18), each one being provided adjacent to a respective the process chamber (13a, 13b), wherein each external air introduction chamber (17, 18) is partitioned with respect to the process chambers (13a, 13b) by the partition plate (12a, 12b), and has an external air introduction port communicated with the air inlet port and the air outlet port.