To facilitate designation of a plotting position even in the state that a circumference is dark by forming a magnifying lens of transparent material and providing a light source for irradiating the lens, in a plotter having the lens to be held at a pen block.

A pen block 11 moving along a rail 10 on a drafting board surface 20 has a base 111, an actuator 112 installed in the base 111, and a pen holder 13 moving vertically by turning ON, OFF the actuator 112. A hole 114 is provided above the holder 113, and a bulb 115 is embedded therein. A switch 117 for turning ON the bulb 115 is provided at the holder 113. A magnifying lens 13 detachably mounted at the holder 113 has an end 121, a part 122 to be held with the holder 113 and a head 124. The lens 13 is formed in a pen shape of a transparent acrylic resin, formed at its vertex of the head 124 in a protrusion state, thereby enlarging the drafting board surface 20 directly under the end 121.