A mold clamping apparatus comprising: a stationary die plate that holds a stationary mold; a movable die plate that holds a movable mold; a die plate moving means (22, 25) that moves the movable die plate toward and away from the stationary die plate; and a mold clamping means that connects and pressurizes the stationary die plate and the movable die plate, wherein the mold clamping means includes a plurality of mold clamping cylinders (18, 18a, 18b, 18c, 18d) provided on one of the stationary die plate and the movable die plate, in that it comprises a plurality of tie bars (17, 17a, 17b, 17c, 17d) each having one end connected to a ram of the mold clamping cylinder, and the other end having a plurality of ring grooves or screw grooves at regular pitches, a plurality of half nuts, each provided on the other of the stationary die plate and the movable die plate and engageable with the plurality of ring grooves or screw grooves, a hydraulic pipe (40, 40a, 40b, 40c, 40d) communicating with each of the plurality of mold clamping cylinders, a hydraulic source including a hydraulic pump (30a, 30b, 30c, 30d) that supplies oil to the hydraulic pipe, and a control device that controls the supply of the oil from the hydraulic source to the hydraulic pipe, and in that the control device controls the supply of the oil based on a mold clamping force by each of the plurality of tie bars (17, 17a, 17b, 17c, 17d) determined correspondingly to an estimated mold opening force by mold internal pressure for molding with mold internal pressure being asymmetrical with respect to a center of a mold block, the mold clamping apparatus being characterized in that the hydraulic pipe (40, 40a, 40b, 40c, 40d) comprises a common pipe (40, 40a, 40b, 40c, 40d), an auxiliary pipe (45a, 45b, 45c, 45d), and a changeover valve (31a, 31b, 31c, 31d) connected to the common pipe (40, 40a, 40b, 40c, 40d) and to the auxiliary pipe (45a, 45b, 45c, 45d), the changeover valve (31a, 31b, 31c, 31d) being supplied oil by the hydraulic source (30a, 30b, 30c, 30d), wherein the control device is configured to control the changeover valve (31a, 31b, 31c, 31d) so as to provide the required amount of oil to the mold clamping cylinder (18a, 18b, 18c, 18d), and in that it further comprises means for performing a flow analysis to estimate the mold internal pressure in advance, and in that the control device is adapted to control the supply of the oil based on the flow analysis performed in advance so that the center of gravity of the mold opening force by the mold internal pressure matches the center of gravity of the mold clamping force by each of the plurality of tie bars (17, 17a, 17b, 17c, 17d). a stationary die plate that holds a stationary mold; a movable die plate that holds a movable mold; a die plate moving means (22, 25) that moves the movable die plate toward and away from the stationary die plate; and a mold clamping means that connects and pressurizes the stationary die plate and the movable die plate, wherein the mold clamping means includes a plurality of mold clamping cylinders (18, 18a, 18b, 18c, 18d) provided on one of the stationary die plate and the movable die plate, a plurality of tie bars (17, 17a, 17b, 17c, 17d) each having one end connected to a ram of the mold clamping cylinder, and the other end having a plurality of ring grooves or screw grooves at regular pitches, a plurality of half nuts, each provided on the other of the stationary die plate and the movable die plate and engageable with the plurality of ring grooves or screw grooves, a hydraulic pipe (40, 40a, 40b, 40c, 40d) communicating with each of the plurality of mold clamping cylinders, a hydraulic source including a hydraulic pump (30a, 30b, 30c, 30d) that supplies oil to the hydraulic pipe, and a control device that controls the supply of the oil from the hydraulic source to the hydraulic pipe, and in that the control device controls the supply of the oil based on a mold clamping force by each of the plurality of tie bars (17, 17a, 17b, 17c, 17d) determined correspondingly to an estimated mold opening force by mold internal pressure for molding with mold internal pressure being asymmetrical with respect to a center of a mold block,