To reduce pressurizing force to hip parts and sigh parts, to remove pressurizing force to a coccyx and to keep a spine to a proper position for reducing the burden of posture keeping muscles by distributing an added load per the unit area of a human body received at the time of sitting.

A buffering sheet with cushion property is stuck to the upper face of a main part at a sitting device. The upper face and the main part side face of the buffering sheet is covered with a surface material 4. A reinforcing plate is stuck to the lower face of the main part. A substrate is fitted to the lower face of the reinforcing plate by including the end part of the material 4. A recessed part 21 is formed at a seat surface 20 on the upper face of the device 1. A hole part 22 is formed at the rear end part of the surface 20 by including a part of the part 21. A raised part 23 positioned between the sigh parts is formed at the center part of the part 21. A line combining P1 and P2 of the part 21 is formed with 4 forward inclination with respect to a horizontal face.