PURPOSE: To detect a frame of a film free from a frame mark by using two sensors which detect picture and non-picture parts of a microfilm simultaneously.

CONSTITUTION: Only case marks (m) are attached to a film F. A detector 11 of a reader/printer is provided with a sensor 23 for detecting the case marks (m), sensors 21, 22 for detecting picture parts and a sensor 20 for detecting non-picture parts 19. When the film is fed after selecting the head of required information by using its case mark, the sensor 20 detects a non-picture part and the sensors 21, 22 detect picture parts, an AND gate 35 is ready to detect frames. When a control signal is inputted to an input terminal 351, the gate is opened and, after a prescribed period, the film is stopped by the action of a brake. Thus, the picture and non-picture parts are detected simultaneously, simplifying the frame detection of a film free from frame marks.