  We prove a formula of Petersson's type for Fourier coefficients of Siegel
cusp forms of degree 2 with respect to congruence subgroups, and as a
corollary, show upper bound estimates of individual Fourier coefficient. The
method in this paper is essentially a generalization of Kitaoka's previous work
which studied the full modular case, but some modification is necessary to
obtain estimates which are sharp with respect to the level aspect.
