The liquid chromatography apparatus and liquid supply device

The present invention provides a liquid delivery device and a liquid chromatography apparatus, which has the kind of the eluent, temperature, mixing ratio, liquid feeding pressure independent accurate manner and with high accuracy low pressure gradients. Comprising: a pump unit, comprising: an eluent having a suction port and discharge port of the cylinder and the reciprocating motion of the piston within the cylinder, having a suction port and a discharge port of the cylinder and reciprocates within said cylinder a piston, a suction above eluent, the discharge; means a valve that switches the type of the plurality of eluate drawn by the pump unit opening and closing operation; a pressure sensor that detects discharged from the discharge outlet of the pump section pressure eluent; a control unit, which controls the opening and closing operation of the valve means, wherein the control unit obtains the above-described eluted from the plurality of suction when suction operation eluate the piston begins to discharge pressure liquid began to be drained until the reduced section, the decompression section and the eluate is actually above drawn actual suction section, performs control so that the valve means in the opening and closing operation of the actual section suction obtained.