To provide a mold clamping device for assembling a mold without using a weight and a molding flask in easy treatment and good workability.

Screw holes fastening a fastening jig 2 are arranged near the outer periphery of a base plate 3. After laying the mold at the regular position on the base plate 3, the fastening jig 2 is covered on the mold. The fastening jig 2 and the base plate 3 are fastened with a fastening means 4 (bolts) and fixed. The structure of the fastening jig 2 fixes plural columns 8 at the lower surface of a connecting plate 6 by welding and arranges pushing plates 10 for clamping the mold near the center of the columns 8. Further, the fastening means 4 with the base plate 3 are arranged at the lower part of the column 8 and fixed to the base plate 3 with the bolts.