To make easily adjustable respectived parts corresponding to a selected sewing in an overlock sewing machine.

On a display plate 1 attached to the arm part of a sewing machine, a kind display column 2 of respective parts to be selected or rejected depending on an operation is provided. A transparent part 3 and a program display part 4 are provided therebelow. On the back side of the transparent part 3, a drum 5 having on its peripheral surface an operation display part 5a corresponding to program numbers and the kind display part is rotatably provided. The rotating shaft of the drum is rotated interlocking with the tension can shaft of an automatic thread adjuster so as to instruct a user to adjust the respective parts corresponding to the selected kind of sewing. Further, an interlocking mechanism is attached so that an adjusting case, an upper looper and a hemstich claw respectively interlock with the setting 2a of a feed stitch, the setting 2f of the upper looper or the setting 2i of the hemstitch claw.