A straddle-type electric vehicle comprising: an electric motor for driving the electric vehicle; a power transmission mechanism for transmitting driving power generated by the electric motor; and a motor unit case including a motor accommodating section for accommodating the electric motor and a transmission mechanism accommodating section for accommodating the power transmission mechanism such that the motor accommodating section and the transmission mechanism accommodating section have a unitary construction; wherein an output shaft of the electric motor extends in a rightward and leftward direction of the vehicle, and one end portion of the output shaft in the rightward and leftward direction is coupled to the power transmission mechanism; and and wherein the transmission mechanism accommodating section of the motor unit case is fastened at right and left sides to a vehicle body frame (8, 9), wherein the motor accommodating section is placed with respect to the transmission mechanism accommodating section in such a manner that the motor accommodating section is, either on the right side or on the left side, joined at one end portion to the transmission mechanism accommodating section and is, on the respective opposite side, not joined at another end portion to the transmission mechanism accommodating section, characterized in that the motor accommodating section is placed in a cantilever state with respect to the transmission mechanism accommodating section, the electric motor has a cylindrical motor case which is accommodated in the motor accommodating section; a peripheral wall portion of the motor accommodating section has a smaller wall thickness than a peripheral wall portion of the motor case which is adjacent to the peripheral wall portion of the motor accommodating section, and a clearance is formed between the peripheral wall portion of the motor accommodating section and the peripheral wall portion of the motor case. an electric motor for driving the electric vehicle; a power transmission mechanism for transmitting driving power generated by the electric motor; and a motor unit case including a motor accommodating section for accommodating the electric motor and a transmission mechanism accommodating section for accommodating the power transmission mechanism such that the motor accommodating section and the transmission mechanism accommodating section have a unitary construction; wherein an output shaft of the electric motor extends in a rightward and leftward direction of the vehicle, and one end portion of the output shaft in the rightward and leftward direction is coupled to the power transmission mechanism; and and wherein the transmission mechanism accommodating section of the motor unit case is fastened at right and left sides to a vehicle body frame (8, 9), wherein the motor accommodating section is placed with respect to the transmission mechanism accommodating section in such a manner that the motor accommodating section is, either on the right side or on the left side, joined at one end portion to the transmission mechanism accommodating section and is, on the respective opposite side, not joined at another end portion to the transmission mechanism accommodating section, characterized in that the motor accommodating section is placed in a cantilever state with respect to the transmission mechanism accommodating section, the electric motor has a cylindrical motor case which is accommodated in the motor accommodating section; a peripheral wall portion of the motor accommodating section has a smaller wall thickness than a peripheral wall portion of the motor case which is adjacent to the peripheral wall portion of the motor accommodating section, and a clearance is formed between the peripheral wall portion of the motor accommodating section and the peripheral wall portion of the motor case.