To provides an apparatus to feed a precoat agent capable of quantitatively charging a precoat agent to a dust collector, stably feeding the precoat agent based on the relationship between the properties of the precoat agent, such as solidification or granulation, and cumulative air blow time with compact structure.

The apparatus to feed a precoat agent comprises a hopper, a replenishing lid, a connecting duct, a nozzle blowing high-pressure air into the hopper, a solenoid valve opening and closing air feed from a source of the high-pressure air, a secondary air suction port taking in the atmospheric air into the hopper. The opening area of the second air suction port is set such that the speed of the air flowing in the connecting duct is within 2 to 5 m/s when the high-pressure air is not blown in from the nozzle, and the number of nozzles is set to be an integer satisfying the range of V50+(0 to 2), for volume V (m3) of a storage volume of the precoat agent in the hopper.