PURPOSE: To prevent the scattering of a powdery hardening-accelerating agent at the time of spraying by mixing a liquid not generating the solidifying reaction with the hardening-accelerating agent with the hardening-accelerating agent before the mixing with a cementitious spray material to wet the hardening- accelerating agent.

CONSTITUTION: The spray material such as water, cement or aggregate introduced into an air pressure sending sprayer 2 from an introducing port 3 is sprayed on a slope 1 from a spray nozzle 4. A hardening-accelerating agent mixed with a liquid 9 is added to the spray material from an addition nozzle 5 by a hardening-accelerating agent pressure sending machine 6. Herein, the liquid 9 is composed of a liquid such as fuel oil not generating the solidifying reaction with the hardening-accelerating agent. Therefore, the hardening- accelerating agent is not scattered from the spray nozzle 4 and the working environment in a spray construction method using no concrete form is well kept.