To provide a sleeper for loading a heavy load, that can improve the load bearing performance while attaining weight reduction.

The sleeper 10 for loading a heavy load that is molded of an extruded material of an aluminum alloy is formed of a pair of beltlike flat plates 11, 12 that are arranged oppositely to each other in the vertical direction, and of a perpendicular plate 13 that is arranged between these flat plate 11, 12 and connects each center in the width direction of these flat plate 11, 12, wherein both side surfaces of the connection part 14 between the flat plates 11, 12 and the perpendicular plate 13 are formed into a concave circular-arcuate shape, with the width W in a cross section surface being set smaller than the height H.