Periodic catatonia (PC) is a rare type of catatonia syndrome, in which the catatonic phases often repeat regularly. Between the catatonic periods, the symptoms totally disappear and make the diagnosis difficult. We report a case with PC who did not show any catatonic symptoms except anxiety and restlessness in his first referral to the hospital. Although it was reported that he showed the symptoms of the disorder such as mutism, and immobility, he was not hospitalized. In his next referral (24 hours later), he was referred with catatonic symptoms and was hospitalized. The periods of catatonia were repeated regularly before electroconvulsive therapy, so the primary diagnosis was PC. During treatment with ECT, based on the semi-structured interview, a diagnosis of bipolar mood disorder was made. Due to the disappearance of symptoms between catatonic periods, this disorder may be underestimated and treatment postponed.