We study linear quadratic optimal control problems for stochastic evolution equations in an infinite horizon with constant coefficients. We first give a characterization of the non-emptiness of the admissible control set for all initial states by an operator-valued algebraic Lyapunov equation. Then we demonstrate the equivalence between the existence of an optimal control with suitable a prori bound and the existence of an optimal feedback control. This stands in contrast to the stochastic linear quadratic optimal control problems in a finite time horizon. Finally, we prove that the optimal feedback control can be determined via a generalized operator-valued algebraic Riccati equation.