A drilling work control method by a drilling work device including a control system controlling drive systems (7, 8) that make a workpiece (50, 60) and a tool that forms a hole in the workpiece (50, 60) execute relative rotating motion and relative feeding motion therebetween, the workpiece (50, 60) includes forming areas (51-56, 61, 62) of a predetermined number that is a plurality divided by being formed of materials of different qualities, the tool forms the hole over two or more working object layers (51a-56a, 61a, 62a, 61b), the drilling work control method comprising: detecting a load torque applied to the tool; determining a working start of drilling work for the workpiece (50, 60); determining two or more forming areas (51-56, 61, 62) respectively in order of drilling work as two or more working object layers (51a-56a, 61a, 62a, 61b) arrayed in a feeding direction that is a direction of the feeding motion based on a times of occurence of variation of the load torque by a predetermined variation coefficient or more after the working start and a layout of the working object layers (51a-56a, 61a, 62a, 61b) of the workpiece preset in the control system; deciding a spindle speed of a rotating motion and feeding speed of the feeding motion corresponding to materials forming the working object layers (51a-56a, 61a, 62a, 61b) that are determined; determining that a working object layer of the working object layers (51a-56a, 61a, 62a, 61b) is a working finishing layer (56a, 61b); determining that the load torque has reduced by a predetermined reduction rate or more; determining that the tool is at an immediately before penetration position that is immediately before penetrating the workpiece (50, 60) in the working finishing layer (56a, 61b) by sensing that a load torque reduction is the predetermined reduction rate or more in the working finishing layer (56a, 61b); controlling the drive systems so that the tool moves forward at a slower speed from the immediately before penetration position to a working finishing position; detecting the working finishing position where the tool penetrates the workpiece (50, 60) and finishes drilling work; and making the feeding speed a slow feeding speed that is slower than a working feeding speed in the working finishing layer (56a, 61b). detecting a load torque applied to the tool; determining a working start of drilling work for the workpiece (50, 60); determining two or more forming areas (51-56, 61, 62) respectively in order of drilling work as two or more working object layers (51a-56a, 61a, 62a, 61b) arrayed in a feeding direction that is a direction of the feeding motion based on a times of occurence of variation of the load torque by a predetermined variation coefficient or more after the working start and a layout of the working object layers (51a-56a, 61a, 62a, 61b) of the workpiece preset in the control system; deciding a spindle speed of a rotating motion and feeding speed of the feeding motion corresponding to materials forming the working object layers (51a-56a, 61a, 62a, 61b) that are determined; determining that a working object layer of the working object layers (51a-56a, 61a, 62a, 61b) is a working finishing layer (56a, 61b); determining that the load torque has reduced by a predetermined reduction rate or more; determining that the tool is at an immediately before penetration position that is immediately before penetrating the workpiece (50, 60) in the working finishing layer (56a, 61b) by sensing that a load torque reduction is the predetermined reduction rate or more in the working finishing layer (56a, 61b); controlling the drive systems so that the tool moves forward at a slower speed from the immediately before penetration position to a working finishing position; detecting the working finishing position where the tool penetrates the workpiece (50, 60) and finishes drilling work; and making the feeding speed a slow feeding speed that is slower than a working feeding speed in the working finishing layer (56a, 61b).