An X-ray photographing apparatus comprising: a generator irradiating an X-ray to a target to be photographed; and a detecting module detecting the X-ray transmitted through the target to be photographed, wherein the detecting module includes: a grid reciprocating between first and second positions; a detector detecting the X-ray transmitted through the grid; and a moving device letting the grid reciprocate, the moving device including: a moving source providing moving force for moving the grid from the first position to the second position; a tension spring providing tension force for moving the grid from the second position to the first position; a coupling member connecting the moving source and the grid to each other so as to transfer the moving force of the moving source to the grid; a guide shaft having a guide part guiding reciprocation of the coupling member; wherein the tension spring has one side fixed to the coupling member and the other side fixed to the guide shaft; wherein the coupling member has a coupling groove formed therein; wherein the moving source includes a motor (243d-1) and a transfer member (243d-2) having a portion inserted into the coupling groove to transfer the moving force of the motor (243d-1) to the coupling member; and the moving device further including: a pressing member pressing the portion of the transfer member (243d-2) inserted into the coupling groove to a wall surface of one side configuring the coupling groove without clearance, wherein said pressing member is a ball plunger inserted into an installation hole of the first coupling member and wherein said pressing member is configured to act as an elastic pressuring member elastically giving pressure to the transfer member (243d-2). a generator irradiating an X-ray to a target to be photographed; and a detecting module detecting the X-ray transmitted through the target to be photographed, a grid reciprocating between first and second positions; a detector detecting the X-ray transmitted through the grid; and a moving device letting the grid reciprocate, the moving device including: a moving source providing moving force for moving the grid from the first position to the second position; a tension spring providing tension force for moving the grid from the second position to the first position; a coupling member connecting the moving source and the grid to each other so as to transfer the moving force of the moving source to the grid; a guide shaft having a guide part guiding reciprocation of the coupling member; wherein the tension spring has one side fixed to the coupling member and the other side fixed to the guide shaft; wherein the coupling member has a coupling groove formed therein; wherein the moving source includes a motor (243d-1) and a transfer member (243d-2) having a portion inserted into the coupling groove to transfer the moving force of the motor (243d-1) to the coupling member; and the moving device further including: a pressing member pressing the portion of the transfer member (243d-2) inserted into the coupling groove to a wall surface of one side configuring the coupling groove without clearance, wherein said pressing member is a ball plunger inserted into an installation hole of the first coupling member and wherein said pressing member is configured to act as an elastic pressuring member elastically giving pressure to the transfer member (243d-2). a moving source providing moving force for moving the grid from the first position to the second position; a tension spring providing tension force for moving the grid from the second position to the first position; a coupling member connecting the moving source and the grid to each other so as to transfer the moving force of the moving source to the grid; a guide shaft having a guide part guiding reciprocation of the coupling member; wherein the tension spring has one side fixed to the coupling member and the other side fixed to the guide shaft; wherein the coupling member has a coupling groove formed therein; wherein the moving source includes a motor (243d-1) and a transfer member (243d-2) having a portion inserted into the coupling groove to transfer the moving force of the motor (243d-1) to the coupling member; and the moving device further including: a pressing member pressing the portion of the transfer member (243d-2) inserted into the coupling groove to a wall surface of one side configuring the coupling groove without clearance, wherein said pressing member is a ball plunger inserted into an installation hole of the first coupling member and wherein said pressing member is configured to act as an elastic pressuring member elastically giving pressure to the transfer member (243d-2).