To attain lightness while maintaining the preventive effect of bedsores or the like and sleeping comfortableness by providing a lamination section overlapped with a flexible resin foam on the surface of a liquid bag filled with a liquid at part of a mat.

A first mat section 11 and a second mat section 12 are connected together on the upper side of an adjoined portion, and the second mat section 12 and a third mat section 13 are connected together on the lower side of the adjoined portion. The second mat section 12 is provided with a urethane foam 122 having a nearly rectangular recess 123 at its center on a similar plastic corrugated fiberboard 121, a liquid bag 124 is mounted in the recess 123 of the urethane foam 122, and a urethane form (polyurethane) 125 is laminated on the liquid bag 124, thereby lightness can be attained while maintaining the preventive effect of bedsores or the like and sleeping comfortableness.