The invention relates to the technical field of sewing machines, in particular to the shell structure of the head of a sewing machine. The shell structure overcomes the problems of installation error, small inner cavity use space, large weight and high cost in the prior art. The technical scheme is as follows: the shell structure of the head of the sewing machine comprises an upper arm, a vertical column, a belt cover and a bottom plate. The shell structure is characterized in that the upper arm consists of an upper cover body and an upper arm body at the lower part; the vertical column consists of an inner column shell and an outer column shell; the upper arm body, the inner column shell and the bottom plate are integrated into a whole structure; the upper cover body, the belt cover and the outer column shell are integrated into a whole structure; and the two integrated structures are connected with each other. Compared with the prior art, the shell structure has the advantages of exact positioning,large use space,good rigidity and low cost.