A device for detecting sleep apnea, the device comprises: a monitoring unit for monitoring an instantaneous output power and an instantaneous rotation speed of a motor delivering air in a breathing device; a calculating unit for obtaining an airway flow reference value represented for the air in an upper airway of a user using the breathing device according to the instantaneous output power and the instantaneous rotation speed of the motor; a first determining unit for determining the user to be in an apnea state when it is determined that the user currently has no spontaneous breathing and corresponding duration has reached a preset time threshold value according to the airway flow reference value; a second determining unit for judging whether the upper airway of the user is clear; and an identifying unit for determining the apnea of the user to be central apnea or obstructive apnea depending on whether the upper airway of the user is clear, wherein the second determining unit superimposes oscillating pressure wave based on the treatment pressure currently supplied by the breathing device to obtain a change amount in flow and pressure after the oscillating pressure wave is superimposed; and determines that the upper airway of the user is blocked when the change amount in flow and pressure exceeds a preset change threshold, otherwise, determines that the upper airway of the user is clear, wherein after the oscillating pressure wave is superimposed, the change amount in flow and pressure is obtained according to an equation as follows: where M is the change amount in flow and pressure, n is a number of cycles of the oscillating pressure wave superimposed on the treatment pressure, V i is a total change amount of the airway flow reference value in each cycle of the oscillating pressure wave, p i is a total change amount of an output pressure in each cycle of the oscillating pressure wave, and k 2 is a constant. a monitoring unit for monitoring an instantaneous output power and an instantaneous rotation speed of a motor delivering air in a breathing device; a calculating unit for obtaining an airway flow reference value represented for the air in an upper airway of a user using the breathing device according to the instantaneous output power and the instantaneous rotation speed of the motor; a first determining unit for determining the user to be in an apnea state when it is determined that the user currently has no spontaneous breathing and corresponding duration has reached a preset time threshold value according to the airway flow reference value; a second determining unit for judging whether the upper airway of the user is clear; and an identifying unit for determining the apnea of the user to be central apnea or obstructive apnea depending on whether the upper airway of the user is clear, wherein the second determining unit superimposes oscillating pressure wave based on the treatment pressure currently supplied by the breathing device to obtain a change amount in flow and pressure after the oscillating pressure wave is superimposed; and determines that the upper airway of the user is blocked when the change amount in flow and pressure exceeds a preset change threshold, otherwise, determines that the upper airway of the user is clear, wherein after the oscillating pressure wave is superimposed, the change amount in flow and pressure is obtained according to an equation as follows: where M is the change amount in flow and pressure, n is a number of cycles of the oscillating pressure wave superimposed on the treatment pressure, V i is a total change amount of the airway flow reference value in each cycle of the oscillating pressure wave, p i is a total change amount of an output pressure in each cycle of the oscillating pressure wave, and k 2 is a constant.