The end-to-end distance of a polymer chain confined between two plates is studied in the presence of the excluded volume interaction using the homotopy parameter expansion method proposed by Oono [Phys. Rev., A30, 986 (1984)]. It is found that ‹Rx2›/‹Rx2›∞, the reduced value of the perpendicular component of mean square end-to-end distance of a perturbed chain is almost the same as that of a Gaussian chain, where ∞ denotes the value of the unconfined chain. The parallel components, ‹Rx2›/‹Rx2›∞ is expressed as ‹Rx2›/‹Rx2›∞=1+c‹Rz2›∞1/2/D, where D is the distance between the plates and c is a quantity slightly depend on D/‹Rz2›∞1/2. The full cross-over behavior and distribution functions of the end-to-end distance for small values of D/‹Rz2›∞1/2 are also presented.