The present invention relates to a fixed quantity discharge device for a liquid container, more specifically a fixed quantity discharge device for a liquid container which includes a contents suction tube extended into the inside of the container body for enabling a pipette tube to be inserted and drawn so as to make the lower end of the pipette tube be exposed to the contents, thus preventing contamination of the pipette tube, and a piston provided in the container body so as to rise as the contents are consumed, thus minimizing the residual contents in the container body.