A method of regulating a servo drive system (1, 101) of a turret punch press machine which uses a servo motor (30a, 30b, 130) as a driving source of a ram (22, 122), wherein the servo motor (30a, 30b, 130) uses a torque based on speed-torque characteristics of the servo motor (30a, 30b, 130) to generate ram pressure, and wherein an operation shaft which vertically moves the ram (22, 122) is directly driven using the servo motor (30a, 30b, 130), comprising: setting the speed-torque characteristics of the servo motor (30a, 30b, 130) in a manner such that a motor torque of the servo motor (30a, 30b, 130), at which a capacity of electric energy supplied by a servo amplifier (40a, 40b, 140a, 140b) is determined, defines the motor torque at which an optimal punching pattern of the ram (22, 122) is generated from a light load to a heavy load according to a type of workpiece to be worked by the turret punch press machine, characterized by further comprising: setting the speed-torque characteristics of the servo motor (30a, 30b, 130) in a manner such that a speed curve and a torque curve rise in a normal rotation direction to constant values, thereby a ram position curve of the ram (22, 122) starts lowering substantially uniformly from an upper end position of the ram (22, 122), when a striker (24, 124) provided at the lower end of the ram (22, 122) pushes a punching die (26, 126) and a tip end of the punching die (26, 126) abuts against an upper surface of a workpiece and the striker (24, 124) receives a load from the workpiece, the torque curve abruptly rises and the speed curve is reduced, thereby the lowering motion of the ram position curve is slowed down, when the tip end of the punching die (26, 126) lowers to a position near to a lower surface of the workpiece and the load received from the workpiece is abruptly reduced, the torque curve abruptly lowers, and the speed curve is accelerated beyond the constant value to restore the speed reduction, thereby the lowering speed of the ram position curve is also accelerated, and in a second half of one cycle of the ram, the ram position curve substantially uniformly rises from the lower end position of the ram (22, 122) to the upper end position of the ram (22, 122). setting the speed-torque characteristics of the servo motor (30a, 30b, 130) in a manner such that a motor torque of the servo motor (30a, 30b, 130), at which a capacity of electric energy supplied by a servo amplifier (40a, 40b, 140a, 140b) is determined, defines the motor torque at which an optimal punching pattern of the ram (22, 122) is generated from a light load to a heavy load according to a type of workpiece to be worked by the turret punch press machine, characterized by further comprising: setting the speed-torque characteristics of the servo motor (30a, 30b, 130) in a manner such that a speed curve and a torque curve rise in a normal rotation direction to constant values, thereby a ram position curve of the ram (22, 122) starts lowering substantially uniformly from an upper end position of the ram (22, 122), when a striker (24, 124) provided at the lower end of the ram (22, 122) pushes a punching die (26, 126) and a tip end of the punching die (26, 126) abuts against an upper surface of a workpiece and the striker (24, 124) receives a load from the workpiece, the torque curve abruptly rises and the speed curve is reduced, thereby the lowering motion of the ram position curve is slowed down, when the tip end of the punching die (26, 126) lowers to a position near to a lower surface of the workpiece and the load received from the workpiece is abruptly reduced, the torque curve abruptly lowers, and the speed curve is accelerated beyond the constant value to restore the speed reduction, thereby the lowering speed of the ram position curve is also accelerated, and in a second half of one cycle of the ram, the ram position curve substantially uniformly rises from the lower end position of the ram (22, 122) to the upper end position of the ram (22, 122). setting the speed-torque characteristics of the servo motor (30a, 30b, 130) in a manner such that a speed curve and a torque curve rise in a normal rotation direction to constant values, thereby a ram position curve of the ram (22, 122) starts lowering substantially uniformly from an upper end position of the ram (22, 122), when a striker (24, 124) provided at the lower end of the ram (22, 122) pushes a punching die (26, 126) and a tip end of the punching die (26, 126) abuts against an upper surface of a workpiece and the striker (24, 124) receives a load from the workpiece, the torque curve abruptly rises and the speed curve is reduced, thereby the lowering motion of the ram position curve is slowed down, when the tip end of the punching die (26, 126) lowers to a position near to a lower surface of the workpiece and the load received from the workpiece is abruptly reduced, the torque curve abruptly lowers, and the speed curve is accelerated beyond the constant value to restore the speed reduction, thereby the lowering speed of the ram position curve is also accelerated, and in a second half of one cycle of the ram, the ram position curve substantially uniformly rises from the lower end position of the ram (22, 122) to the upper end position of the ram (22, 122).