PURPOSE: To construct a gate switching drive mechanism with simple structure by forming a driving means, for driving each gate member corresponding to each bin, of operating members for driving the gate members, cam members for rotating the operating members, and a detecting control part for detecting/ controlling the position of the cam members.

CONSTITUTION: A collator 10 is formed of a conveyor part 18 for conveying a recording medium 5, numerous bins 20, gate members 21 corresponding to the respective bins 20, a switching drive mechanism for rotating the gate members 21 by operating members 23 and cam mechanism 35, and a detecting control part 45 for detecting/controlling the mechanism 35. The gate member 21 fittingly fixed at a gate rotating pivot 22 provided in a position corresponding to each bin 20 is rotated in the direction of opening a sheet carrier path 16 by an unillustrated spring. The operating means 23 for rotating the gate member 21 is rotated by a disc cam 30, and a disc cam rotating pivot 31 is rotated normally and reversely by a drive source 36. The detecting control part 45 for detecting/controlling the rotational position of the cam 30 is provided with a sensor disc 40 and a detecting part thereof.