PURPOSE: To eliminate pulsation of discharge rate in a simple structure, and to discharge a fixed quantity of liquid with high pressure in proportion to the rotating speed.

CONSTITUTION: A quantitative discharge device 100 comprises two double-acting plunger pumps 1, 2, and a cam mechanism 3 for accelerating the plungers 4, 5 of the respective double-acting plunger pumps 1, 2 at the uniform acceleration from the bottom dead center to 90 degrees, decelerating the same at the uniform deceleration from 90 degrees to the top dead center, accelerating the same at the uniform acceleration from the top dead center to 270 degrees, and decelerating the same at the uniform acceleration from 270 degrees to the bottom dead load. The cam mechanism 3 drives the respective plungers 4, 5 with the phase thereof shifted by 90 degrees to fix the sum of discharge rates of two double-acting plunger pumps 1, 2.