<p>A new locally operated unilateral master-slave manipulator for endoscopic surgery performed by a surgeon in a sterilized area was developed. The manipulator system consists of a portable master device and a forceps slave manipulator (revised parallel-linkage mobile LODEM) as the third arm. We propose the mechanically separable portable device which can be set anywhere beside the operating table. The master device consists of a portable mechanical part that can be autoclave sterilized and an encoder sensor part connected to driving wires covered with a coiled steel flexible cable tube. The five-DOFs master devices use a magnetic ball joint and gimbals for the pitch and yaw axes, a linear guide for the insertion axis, a circular dial for the roll axis, and a handle for the grasp axis. The dimensions of the mechanical component are 130 mm × 130 mm × 350 mm, and its mass is 1.0 kg. The operating ranges for these axes are ±70 °, ±70 °, 100 mm, ±180 °, and 40 °, respectively. The mechanical backlash is 0.8 ° to 4.9 ° for the pitch and yaw axes, and 0.6 mm to 2.6 mm for the insertion axis. The modified mobile LODEM, which is used as the slave manipulator, is unilateral master-slave controlled by the master device. The master-slave manipulator was confirmed for the pitch, the yaw, the insertion, and the roll axes when the velocities are 15 °/s, 15 °/s, 50 mm/s, and 1080 °/s, respectively. Simulated laparoscopic cholecystectomy was performed on a surgically realistic model in a training box by an endoscope specialist. The forceps slave manipulator was driven under the surgeon’s master-slave control using the portable master device. The experimental results indicate that 5 mm backlash at the handle of master device is not large for the master-slave manipulator as the assistant. The results of the present study suggest that the proposed system could be used for robotically assisted laparoscopic surgery by a surgeon working near the patient.</p>