We investigated the effect of Sm3+ substitution on the crystalline quality and transport properties of "infinite layer" SrFeO2 epitaxial thin films. Sm-substituted SrFeO2 (Sr1-xSmxFeO2) films were prepared via a topotactic reaction using CaH2 on KTaO3 (KTO) and DyScO3 (DSO) substrates. The films exhibited metallic behavior with higher conductivity than the undoped ones on both KTO and DSO. The carrier density of the Sm-substituted film was much lower than the Sm3+ concentrations, suggesting that the electron carriers generated by Sm were mostly compensated by excess oxide ions residing at the apical sites of Fe. The Sm-substitution also enhanced the crystalline quality of the films, probably because the excess oxide ions stabilized the framework of the infinite layer structure. We found a strong correlation between the conductivity and the crystalline quality in the films, indicating that the conductivity of Sm-substituted SrFeO2 was dominated by the crystalline quality. Furthermore, a high Hall mobility of 13.5 cm2 V-1 s-1 was achieved at 300 K in the x = 0.05 film.