Transmission and reflection measurements using synchrotron radiation have been performed on a Ni sample submitted to tensile stress. For each studied crystalline plane, the strain was determined from spectral analysis of the diffracted beam, with a precision in the range of goniometric X-ray analysis. Apparent elasticity characteristics were then deduced assuming plane stress state on the surface and plane strain state in the bulk. The high elasticity modulus at the surface compared with the bulk one could be explained by a roughness effect or a lower yield stress near the surface.