PURPOSE: To provide a postal matter treatment device which performs precisely detection of an initial position of stamping member and can contrive damage prevention of the postal matter, damage prevention of a mechanism part and simplification of operation.

CONSTITUTION: A stamping hub 15 which is contained in a detecting-stamping part performs stamping operation. A disk 17 provided on a stamping hub 15 in a coaxial state is provided with a shaft fitting part 17a having a form obtained by combining two kinds of a large and small semicircular plates with each other and a notch part 17b is provided in a part of an outer circumference of the shaft fitting part 17a. Then an initial position sensor 18 is provided with a light emitting element and light receiving element and a light path passing through the notch part 17b is formed in a vertical direction to the disk 17. Then stop timing sensor 19 also is provided with the light emitting element and light receiving element and the light path is formed in the vertical direction to the disk 17.