An investigation on the mass transfer for a two-dimensional jet of air impinging normally on a flat plate was undertaken. Results are summarized as follows. (1) Sherwood numbers at the stagnation point obtained experimentally are about twice those predicted by theory. This fact is due to the turbulence of jet itself. (2) By assuming the flow field on a plate simulated by the wall jet having an imaginary slot at the stagnation point and by applying Myer's theory concerning the heat transfer of the wall jet, we obtained the theoretical prediction for local Sherwood numbersm which agree well with experimental data. (3) Gardon's postulate that mean Sherwood number is correlated by the arrival Reynolds number was checked by the present experiment and discussed under the theoretical background.