To attain high-speed needle swinging operation by reducing force applied to a journal part in a mechanism in needle swinging operation.

This buttonholing sewing machine includes a needle bar vertical driving mechanism for vertically moving a needle bar, and a needle swinging mechanism for swinging the needle bar synchronously with the needle bar vertical driving mechanism. The needle swinging mechanism includes a needle bar guide part through which the needle bar is slidably inserted; a first journal part surrounding the needle bar guide part and journaling the needle bar guide part turnably and slidably on both side across the needle bar so that the needle bar guide part turns around a direction, orthogonal to the axial direction of the needle bar, as a turning axis and slides in a direction of the turning axis of the needle bar guide part; and a second journal part holding the first journal part by a pair of support pieces in an extending direction of the turning axis of the first journal part to journal the first journal part turnably and slidably so that the first journal part turns around a direction, orthogonal to both the axial direction of the needle bar and the turning axis of the first journal part, as a turning axis and that the first journal part slides in the turning axis direction.