To reduce the possibility of the erroneous detection of a frame in a microfilm retrieving device executing retrieval by detecting the existence of the frame from a change in the density of microfilm in a traveling direction.

This device is provided with an encoder outputting a sampling signal for every specified feed rate of the microfilm 26, plural density sensors 108 detecting film density at positions which are on a straight line orthogonal with the traveling direction of the microfilm 26 and also are different in the width direction of the frame in the track width of a traveling shaft, a binarizing part 110 binarizing a density signal that is the output of the density sensor 108 by synchronizing with the sampling signal, a discriminating part 112 discriminating the existence of the frame based on plural binarization signals and outputting a discriminated signal and a retrieving part 114 executing the retrieval of the frame based on the discriminated signal.