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We study the Maxwell field with a general gauge fixing (GF) term in theradiation-dominant (RD) and matter-dominant (MD) stages of expanding Universe,as a continuation to the previous work in de Sitter space. We derive the exactsolutions, perform the covariant canonical quantization and obtain the stresstensor in the Gupta-Bleuler (GB) physical states, which is independent of theGF constant and is also invariant under the quantum residual gaugetransformation. The transverse stress tensor is similar in all flatRobertson-Walker spacetimes, and its vacuum part is $\propto k^4$  and becomes zero after the 0th-order adiabatic regularization. Thelongitudinal-temporal stress tensor, in both RD and MD stages, is zero due to acancelation between the longitudinal and temporal parts in the GB states, andso is the particle part of the GF stress tensor. The vacuum GF stress tensor,in the RD stage, contains $k^4,k^2$ divergences and becomes zero by the2nd-order regularization, however, in the MD stage, contains $k^4, k^2, k^0$divergences and becomes zero by the 4th-order regularization. So, the order ofadequate regularization depends not only upon the type of fields, but also uponthe background spacetimes. In summary, in both the RD and MD stages, like in deSitter space, the total regularized vacuum stress tensor is zero, only thetransverse photon part remains, and this holds independent of the GF term.

Maxwell field with gauge fixing term in the radiation- and matter-dominant stages: exact solution and stress tensor