A multi-step regeneration apparatus of a diesel particulate filter, which generates a load to an engine to remove soot, the apparatus comprising: an external air temperature sensor configured to measure a temperature of external air; a controller configured to compare a temperature value measured by the external air temperature sensor with a predetermined value and output a signal; and a control valve unit; wherein the multi-step regeneration apparatus is characterised in that the control valve unit includes a first control valve and a second control valve receiving the signal from the controller, and a first spool operated by the first control valve and a second spool operated by the second control valve, wherein the control valve unit further includes a first relief valve having a set pressure and a second relief valve having a set pressure positioned at rear ends of the first spool and the second spool, and the set pressure of the second relief valve is larger than the set pressure of the first relief valve, and wherein when the temperature value measured by the external air temperature sensor is larger than the predetermined value, the controller is configured to apply a voltage to the first control valve to open the first spool, and a pressure of a working fluid discharged from a main pump is increased to the pressure while the working fluid passes through the first relief valve, wherein when the temperature value measured by the external air temperature sensor is smaller than the predetermined value, the controller is configured to apply a voltage to the first control valve and the second control valve to open both the first spool and the second spool, and the pressure of the working fluid discharged from the main pump is increased to the pressure while the working fluid passes through the first spool and the second spool and then through the second relief valve. an external air temperature sensor configured to measure a temperature of external air; a controller configured to compare a temperature value measured by the external air temperature sensor with a predetermined value and output a signal; and a control valve unit; wherein the multi-step regeneration apparatus is characterised in that the control valve unit includes a first control valve and a second control valve receiving the signal from the controller, and a first spool operated by the first control valve and a second spool operated by the second control valve, wherein the control valve unit further includes a first relief valve having a set pressure and a second relief valve having a set pressure positioned at rear ends of the first spool and the second spool, and the set pressure of the second relief valve is larger than the set pressure of the first relief valve, and wherein when the temperature value measured by the external air temperature sensor is larger than the predetermined value, the controller is configured to apply a voltage to the first control valve to open the first spool, and a pressure of a working fluid discharged from a main pump is increased to the pressure while the working fluid passes through the first relief valve, wherein when the temperature value measured by the external air temperature sensor is smaller than the predetermined value, the controller is configured to apply a voltage to the first control valve and the second control valve to open both the first spool and the second spool, and the pressure of the working fluid discharged from the main pump is increased to the pressure while the working fluid passes through the first spool and the second spool and then through the second relief valve.