There is provided a compression device for living being, simply structured and capable of fitting a site to be measured of any size. The compression device includes an elastic plate formed in one piece and elastically holding a predetermined curvature, provided for preventing a fluid bag from expanding outwards. The elastic plate includes a first curvature substantially matching a lateral cross section of a thin site to be measured, a second curvature and a connection connecting the first and second curvatures together. The connection allows the second curvature to be arranged outwardly of a virtual extension of the first curvature substantially matching the lateral cross section of the thin site to be measured. The second curvature extends inwardly of a virtual extension of the connection extending toward the second curvature.