Pit craters on Mars are a good target for a Mars exploration because of scientific and engineering reasons. This study conducts a conceptual design and proposes a multicopter type exploration probe for the pit crater on the Martian surface. Especially, the effects of the number of the rotors (i.e., quad, hexa, octa, deca-copter.) on the standard design and maximum load design were investigated. The designable range enlarged with the increase of the number of the motor, but the trend gradually saturated. When the mission condition was the same, the design with the designable lowest number of motors showed the smallest size. As a result, a quadrotor type Mars helicopter design is presented.