The invention provides a shaft for a roller wheel which is excellent in strength and can achieve a weight saving. The invention provides a shaft for a roller wheel which rotatably supports a roller (3) outward fitted between both end portions (5a, 5b) in a state in which both end portions (5a, 5b) are fixed, and receives a load in a diametrical direction via the roller (3). Recess portions (6, 6) are provided on a side to which the load is not applied, on an outer peripheral surface corresponding to the roller (3). The load applying direction is a vertical direction. A cross sectional shape of the shaft in the recess portions (6, 6) is formed in a shape which is constituted by an upper circular arc portion (10) on an upper side, a lower circular arc portion (11) on a lower side, and a vertical connection portion (12) passing through a shaft axis (O) and connecting the upper circular arc portion (10) to the lower circular arc portion (11).