To provide an air blast device capable of continuously performing injection processing, while replenishing an abrasive, without causing a bridge phenomenon in an opening part when replenishing the abrasive and leakage of air in a vessel.

This air blast device forcibly feeds a mixture to an external part by mixing the abrasive with compressed air supplied from the external part; and has a pressurizing vessel 2 having an opening part 8 in an upper part, an abrasive vessel 1 airtightly connected to the opening part 8 and replenishing the abrasive to the pressurizing vessel 2, a replenishing valve 3 openable and closable by fitting to the opening part 8 from the inside of the pressurizing vessel 2, a first electromagnet 12a arranged outside the abrasive vessel 1, a rod 9 rotatably supported in the abrasive vessel 1 so as to be freely movable in the shaft direction and to be freely rotatable around its shaft, provided with a first magnetic substance 11a on one end side, having the other end side connected to the replenishing valve 3, exerting attracting force on the first magnetic substance 11a by power supply to the first electromagnet 12a and constituted so as to open and close the opening part 8 by the replenishing valve 3, and a rotary mechanism for rotating around a shaft of the rod 9.