  Affine analogue of Jack's polynomials introduced by Etingof and Kirillov Jr.
is studied for the case of \hat{sl}_2. Using the Wakimoto representation, we
give an integral formula of elliptic Selberg type for the affine Jack's
polynomials. From this integral formula, the action of SL_2(Z) on the space of
the affine Jack's polynomials is computed. For simple cases, we write down the
affine Jack's polynomials in terms of some modular and elliptic functions.
