Comments on SUSY Exact Action in 3D Supergravity

We consider 2+1 dimensional off-shell N = 1 pure supergravity that is constructed from graviton, gravitino and auxiliary field. We show that the $R^2$ supersymmetric invariant and $R^2_{\mu \nu}$ supersymmetric invariant are expressed as local supersymmetric exact terms up to mass terms for gravitino. In both cases, the mass parameter is proportional to the off-shell supersymmetric cosmological constant.