To take a preferable sleeping posture without any burden on the backbone, prevent the occurrence of a bedsore, and maintain high comfort and enough gas permeability by forming granular resin materials to have a movable spherical or elliptical shape for forming a support plane well fit to the body of a person lying thereon.

A cover cloth 1a is filled with elastic granular resin material 3. In this case, the granular resin material 3 may be hollow ball type or solid ball or elliptical body type, or the ball or elliptical ball body may be made of expanded resin, using material such as expanded styrene, expanded neopolyprene, and expanded urethane. Also, the expanded resin is available in the form of continuous expanded or independently expanded type. When a person lies on a mattress 1, the granular resin material 3 shows mobility for moving from a strong body pressure position to a low body pressure position, depending on the irregularities of a body, within mattress internal space separated with a partition 4 and limited with connecting parts 5, thereby providing a support plane 8 fit to the body at suitable elasticity, and dispersing and bearing body pressure almost homogeneously.