The invention relates to a device for dotting internal circular surfaces in the machining technical field, which is characterized in that one end of a tool bar is provided with a cuboid through hole in which a motion converter is arranged; a dotting tool is arranged on the motion converter; the other end of the tool bar is provided with a tool bar connector; a full-length straight groove is cut onthe tool bar; a pulling rod is arranged in the straight groove on the tool bar; a bearing support is connected with the connector on the tool bar by bolts; a cross groove is cut at the tail of the pulling rod and internally provided with a pulley device; a spring is arranged at the tail of the pulling rod and leans against the end part of the tool bar; the other end of the spring leans against the step of a cross groove at the head of the pulling rod; a wire contact pair is formed between a bearing and an eccentric wheel; and the dotting tool converts the horizontal motion of the pulling rodinto the vertical motion of the tool by the motion converter. The device is capable of dotting the surface inside a circular hole with a relatively small diameter and regulating the depth and distribution rule of the dotted points, and has the advantages of simple operation, convenient repair and low machining cost of machined parts, thus being widely applicable to actual production.