Schizophrenia (SCZ) is a severe psychiatric disorder characterized by positive symptoms, negative symptoms, and cognitive deficits. Although its pathoetiology remains unclear, it is known to involve small GTPase signaling. Rho kinase, an effector of small GTPase Rho, is highly expressed in the brain and plays a major role in neurite elongation and neuronal architecture. This study used a touchscreen-based visual discrimination (VD) task to investigate the effects of Rho kinase inhibitors on cognitive impairment in a methamphetamine (METH)–treated mouse model of SCZ. Systemic injection of the Rho kinase inhibitor fasudil dose-dependently ameliorated METH-induced impairment of VD. Fasudil also significantly suppressed the increase in the number of c-Fos–positive cells in the medial prefrontal cortex (mPFC) and dorsomedial striatum (DMS) following METH treatment. Bilateral microinjections of Y-27632, the other Rho kinase inhibitor, into the mPFC or DMS significantly ameliorated the METH-induced impairment of VD. Two proteins downstream of Rho kinase, myosin phosphatase-targeting subunit 1 (MYPT1; Thr696) and myosin light chain kinase 2 (MLC2; Thr18/Ser19), exhibited increased phosphorylation in the mPFC and DMS, respectively, after METH treatment, and fasudil inhibited these increases. Both haloperidol and fasudil ameliorated the METH-induced impairment of VD, while clozapine had little effect. Both haloperidol and clozapine suppressed METH-induced hyperactivity, but fasudil had no effect. Finally, haloperidol and clozapine significantly suppressed the METH-induced increase in MYPT1 (Thr696) phosphorylation in the mPFC, but not in the DMS. Thus, the METH-induced cognitive function impairment was ameliorated by treatment with Rho kinase inhibitors, which may act via the cortico-striatal circuit.