A two-hole core drilling machine of the invention includes a body, a vertically reciprocating carriage vertically reciprocably mounted to the body, a fixing plate coupled to one side surface of the carriage, to rotatably support a drive shaft of a motor, a pivoting plate fastened to the fixing plate under a condition that a pivot angle of the pivoting plate is changed, a moving plate fastened to the pivoting plate under a condition that a length of the moving plate from the pivoting plate is varied, a belt or chain mounted between a drive pulley coupled to the drive shaft and a driven pulley coupled to a driven shaft rotatably mounted to the moving plate, a first core bit coupled to the drive shaft, and a second core bit coupled to the driven shaft.

A four-hole core drilling machine of the invention includes a vertically reciprocating carriage mounted to a body, a motor coupled to the carriage, a fixing plate coupled to the carriage, to rotatably support a drive shaft of the motor, a pivoting plate fastened to the fixing plate under the condition that a pivot angle of the pivoting plate is changed, a drive pulley coupled to the drive shaft, to be rotatable by the drive shaft, four driven pulleys rotatably mounted to the pivoting plate near corners of the pivoting plate, four driven shafts rotatably mounted to the pivoting plate and coupled to the four driven pulleys, to be rotatable by the driven pulleys, a belt mounted around the drive pulley and the driven pulleys, to transmit rotation force of the drive pulley to the driven pulleys, and four core bits coupled to lower ends of the driven shafts.