PURPOSE: To provide a tapered bore working machine capable of making a tapered bore precisely at one time of bore work per sheet even in a pliable sheet material of plastic or the like.

CONSTITUTION: In a tapered bore working machine 1, following processes are repeated so that respective means is controlled by sequence control means 80. At first, pulling-out cylinders 70a, 70b push out a vinyl chloride sheet at the supply position 101 and, simultaneously, a pushing-up cylinder 20 pushes up the laminated vinyl chloride sheets to a walling position 102, and thereby an unfinished vinyl chloride sheet 100 comes into the lowermost layer. Subsequently, pushing-out means 10 pushes out the unfinished vinyl chloride sheet 100 at the lowermost layer under the vinyl chloride sheet at the working position 104, and after the drill blade 38 of a drilling machine 30 effects tapered bore work on the upper one sheet, pushing-back cylinder 50 pushes back the upper one sheet to the waiting position 102. The pliable sheet material is supported at all times by the lower unfinished pliable sheet material and, therefore, the tapered bore never deforms even in the final stage of the tapered bore work.