The present invention provides: a novel compound which has a useful pharmacological action for treating heart failure or shock without increasing heart rate; and a pharmaceutical composition using the same. The present invention relates to a diphenylmethyl piperazine derivative represented by general formula (I) (In the formula, R1 is a hydrogen atom or a hydroxy group. R2 is a hydrogen atom, a halogen atom, a hydroxy group, an alkyl group having one to five carbon atoms, or an alkoxyl group having one to five carbon atoms, excluding the case where R1 is a hydroxy group and R2 is a chlorine atom.) or a pharmaceutically acceptable salt thereof, and a pharmaceutical composition containing the same.