A linear guide mechanism configured to slidably support a moving block on an actuator, the linear guide mechanism comprising: an actuator side guide member attached to the actuator; a pair of moving block side guide members disposed on both sides of the actuator side guide member; wherein the moving block side guide members are made from a heat-treated steel; a plurality of balls; and a pressing mechanism configured to adjust a pre-loading of the balls and improve straightness of the moving block side guide members, is attached to the moving block, characterized in that the pair of moving block side guide members is attached to the moving block, the plurality of balls is disposed in two rows, respectively, between the actuator side guide member and each of the moving block side guide members, wherein the actuator side guide member includes circulation holes (34a to 34d) through which the balls circulate, the pressing mechanism is a plurality of set screws, and the set screws are arranged alongside one another in a longitudinal direction of the side wall portion of the moving block, the set screws are respectively screwed into screw holes penetrating through the side wall portion of the moving block, and distal ends of the set screws abut against an outer side surface of the moving block side guide members, the linear guide mechanism further comprises a plurality of fastening bolts configured to fix each of the moving block side guide members to the moving block and improve the straightness of the moving block side guide members, wherein axes of the fastening bolts and axes of the set screws are in a positional relationship of being perpendicular to each other when viewed from a direction along a sliding direction of the moving block, and the fastening bolts are arranged alongside one another in a longitudinal direction of the moving block side guide members. an actuator side guide member attached to the actuator; a pair of moving block side guide members disposed on both sides of the actuator side guide member; wherein the moving block side guide members are made from a heat-treated steel; a plurality of balls; and a pressing mechanism configured to adjust a pre-loading of the balls and improve straightness of the moving block side guide members, is attached to the moving block, characterized in that the pair of moving block side guide members is attached to the moving block, the plurality of balls is disposed in two rows, respectively, between the actuator side guide member and each of the moving block side guide members, wherein the actuator side guide member includes circulation holes (34a to 34d) through which the balls circulate, the pressing mechanism is a plurality of set screws, and the set screws are arranged alongside one another in a longitudinal direction of the side wall portion of the moving block, the set screws are respectively screwed into screw holes penetrating through the side wall portion of the moving block, and distal ends of the set screws abut against an outer side surface of the moving block side guide members, the linear guide mechanism further comprises a plurality of fastening bolts configured to fix each of the moving block side guide members to the moving block and improve the straightness of the moving block side guide members, wherein axes of the fastening bolts and axes of the set screws are in a positional relationship of being perpendicular to each other when viewed from a direction along a sliding direction of the moving block, and the fastening bolts are arranged alongside one another in a longitudinal direction of the moving block side guide members.