A door closure structure for a rotary door rotatably mounted on a main body, comprising: a hinge assembly, wherein the rotary door is mounted on the main body via the hinge assembly, and the hinge assembly comprises: a hinge body fixed on the main body in a longitudinal direction; a hinge plate provided with a hinge hole and connected with a rear end of the hinge body; and a hinge shaft fitted with the hinge hole; a supporting plate extended in a lateral direction, provided with a first hole and connected with a front end of the hinge body; a mask body fixed on the rotary door in a mounting recess, wherein a mask cavity is defined in the mask body and a second hole is disposed in a surface of the mask body, a first surface of the mask body being open; and an engaging block retractably and movably disposed in the mask cavity, wherein a part of the engaging block is exposable out of the mask body from the second hole and the part of the engaging block extended out of the mask body is engagable with the first hole to make the rotary door close the main body; a cover plate disposed on the first surface of the mask body to close the first surface, in which the second hole is formed in the cover plate, a receiving space being defined by the cover plate and the mounting recess; an elastic member disposed between the mask body and the cover plate pushes the engaging block to move downwards to make a part of the engaging block exposed out of the mask body from the second hole of the cover plate; and a groove communicated with the first surface is formed in a second surface of the mask body adjacent to the first surface of the mask body; wherein the supporting plate is adapted to be inserted from the groove into the receiving space for fitting the first hole with the engaging block. a hinge assembly, wherein the rotary door is mounted on the main body via the hinge assembly, and the hinge assembly comprises: a hinge body fixed on the main body in a longitudinal direction; a hinge plate provided with a hinge hole and connected with a rear end of the hinge body; and a hinge shaft fitted with the hinge hole; a hinge body fixed on the main body in a longitudinal direction; a hinge plate provided with a hinge hole and connected with a rear end of the hinge body; and a hinge shaft fitted with the hinge hole; a supporting plate extended in a lateral direction, provided with a first hole and connected with a front end of the hinge body; a mask body fixed on the rotary door in a mounting recess, wherein a mask cavity is defined in the mask body and a second hole is disposed in a surface of the mask body, a first surface of the mask body being open; and an engaging block retractably and movably disposed in the mask cavity, wherein a part of the engaging block is exposable out of the mask body from the second hole and the part of the engaging block extended out of the mask body is engagable with the first hole to make the rotary door close the main body; a cover plate disposed on the first surface of the mask body to close the first surface, in which the second hole is formed in the cover plate, a receiving space being defined by the cover plate and the mounting recess; an elastic member disposed between the mask body and the cover plate pushes the engaging block to move downwards to make a part of the engaging block exposed out of the mask body from the second hole of the cover plate; and a groove communicated with the first surface is formed in a second surface of the mask body adjacent to the first surface of the mask body; wherein the supporting plate is adapted to be inserted from the groove into the receiving space for fitting the first hole with the engaging block.