The invention relates to a press machine crank eccentricity adjusting device. The device comprises a crank and is characterized in that two ends of the crank are connected to a crank mounting device through support devices and bearings; each support device is provided with two plungers connected with the crank, and the plungers and the crank are coordinated to form a sealed oil cavities A and C and sealed oil cavities B and D, the sealed oil cavity A and the sealed oil cavity B are communicated through a flow channel in the crank, and the sealed oil cavity C and the sealed oil cavity D are communicated through a flow channel in the crank; a flow distribution device is mounted at the tip of the crank and provided with two oil channels, and the two oil channels are respectively communicatedwith the sealed oil cavities A and B and the sealed oil cavities C and D; the outer side of the support device at the other end of the crank is connected with the drive device of a press machine to transmit torque and rotation speed to the crank, and the crank is driven by the acting force to rotate. The press machine crank eccentricity adjusting device has the advantages that by controlling the quantity of oil entering the sealed oil cavities A and B and the sealed oil cavities C and D, the relative position between the crank and a machine body can be adjusted so as to adjust the eccentricity.