PURPOSE: To provide a sheet conveying device capable of detecting surely the thickness of sheet and multiple feeding even if sheets are moved irregularly or swung.

CONSTITUTION: This sheet conveyor is provided with two separate rollers 13 and 13 separating sheets of paper 12 piece by piece, and three conveyor rollers 14, 14' and 14" conveying the separated paper 15, and in this constitution, two position sensors 18 and 19 as distance measuring means measuring a distance from the paper 15 are installed at both sides of the paper 15 during conveyance, and the sum of the measured value is subtracted from a distance between both these position sensors 18 and 19, whereby thickness of the paper 15 is detected.