The single needle switching device (1) comprises: the switching lever (2) for performing the switching operation of a needle bar to be used when performing sewing by one or both of the pair of needle bars provided on a sewing machine; a switching mechanism (18) connected to the switching lever (2), for making two-needle sewing or one-needle sewing by one of the needles possible in linkage with the operation of the switching lever (2); a release lever (19) for releasing the switching mechanism (18) to the state of performing two-needle sewing by both needle bars when the switching mechanism (18) is in the state of performing one-needle sewing by one of the needle bars by the operation of the switching lever 2; a pressurizing mechanism (6) for directly or relatively imparting pressurizing force to the switching lever (2) or the switching mechanism (18); and an adjusting mechanism (7) provided in the pressurizing mechanism 6 for adjusting the pressurizing force to the switching lever (2) or the switching mechanism (18). |