To provide a throat plate structure of a sewing machine capable of surely tightening seams by sufficiently pulling up an upper yarn, assuring cloth holding function of holding a cloth workpiece and improving the quality of a sewed product.

A auxiliary throat plate member 112 formed integrally with a base 113 in a sectionally circular shape and an annular protrusion 114 on the outer periphery of the base 113 is fixed to the upper face of the front end of a throat plate 110 with a pair of machine screws. The protrusion 114 is annularly provided about a needle hole 111 near the needle hole in the upper face of the throat plate 110, wherein an upper yarn floating gap 116 in communication with the needle hole 111 is formed in a space to the lower end of a cloth holder 120 at a bottom dead point or to the lower end of the cloth holder 120 accepted on the flat face 114a of the protrusion 114 with a recess 115 stepwisely recessed lower than the upper end of the protrusion 114.