body 41 and pressurizes a bobbin thread 46 a bobbin thread guiding slot 48 is formed in portion 47 as shown in fig1 the bobbin thread 46 is passed through the bobbin thread guiding slot 48 and is elastically pressed against the side face 41a by the pressurizing portion 47 by turning the adjustment screw 45 in opposite directions the force acting on the bobbin thread can be adjusted therefore it is possible to apply a proper tension by the rotary action of the rotating hook 23 to the bobbin thread 46 removed from the bobbin 25 thereby ensuring a sewing operation conducted with a desired thread tension fig1 is a perspective view of a bobbin holding member 60 illustrative of the third embodiment of the invention a body 61 of the bobbin holding member 60 has integrally formed therewith a bobbin thread guiding member 62 the bobbin thread guiding member 62 has formed therein a notch 63 through which fits the bobbin thread 46 the bobbin thread 46 removed from the bobbin 25 passes through the bobbin thread guiding slot 48 is elastically pressed by the pressurizing portion 47 against a side face 61a of the body 61 and is passed through the notch 63 this.