To provide a segment made of steel, in which the flexural rigidity of a joint bar is increased largely, the segments made of steel adjacent in the circumferential direction of a tunnel can mutually be joined surely and firmly and high cutoff properties can be held.

The segment made of steel has a plurality of main girders 1 connected in the circumferential direction of a tunnel and joint bars 2 connected in the axial direction of the tunnel at both end sections of the main girders 1 respectively. The joint bars 2 are formed while having a plurality of cross ribs 2a connected in parallel in the axial direction as ribs and a plurality of longitudinal ribs 2b connected in the axial rectangular direction and joint ribs 2c projected to the main-girder side from both end sections in the axial direction respectively. The joint bars 2 are formed by casting.