PURPOSE: To stabilize a liquid supply amount from a pump as a liquid supply means and to improve precision of a mixing ratio in a multiple liquid (two liquid) mixing device.

CONSTITUTION: Valves 991, 993 are provided free to close a passage 971A constituting a liquid supply route from a main agent-hardening agent pump to a mixer, and diaphragms 981, 983 to actuate these valves in accordance with introduction of back pressure to a part 955 are provided. The degree of the back pressure is properly specified in accordance with stable working pressure of the pump, that is, liquid supply pressure, and when the liquid pressure is low and unstable, by the work of the back pressure, the valves 991, 993 close the passage 971A.