To provide a sewing device for tatami mats, which can easily switch between ladder stitching and trapezoid stitching which is suitable for thin tatami mats.

A control device 81 has function to perform ladder stitching, trapezoid stitching which is suitable for thin tatami mats, variant zigzag stitching, serrated stitching, reversed serrated stitching and straight stitching by controlling a needle motor 19, a feeding motor 15 and a cylinder 41 based on input signals from the respective switches 77, 79, 80 and the respective sensors 30, 43, 44 and a control program installed in advance. Then, plural stitching methods can be easily switched without doing difficult things like exchanging and converting machine parts such as a cam or the like.