The invention provides a measuring apparatus for the concentrations of nitric oxide and carbon monoxide in expired air. The measuring apparatus is composed of a sampling module and an analysis module. The sampling module is formed by tandem connection of a flow regulator, a stop valve and a sampling pump, wherein the flow regulator is connected with a flow/pressure sensor and a CO2 sensor, and a group consisting of an air chamber I, a solenoid valve I and a solenoid valve VI and a group consisting of an air chamber II, a solenoid valve II and a solenoid valve VII are arranged between the flow/pressure regulator and the sampling pump in a parallel connection manner, the solenoid valve I and the solenoid valve VI are connected with the air chamber I and respectively located before and behind the air chamber I, and the solenoid valve II and the solenoid valve VII are connected with the air chamber II and respectively located before and behind the air chamber II. A circulation air path is formed in the analysis module by the air chamber I, the solenoid valve I or the air chamber II, the solenoid valve II, a tee valve I, an analysis pump, a tee valve II, an air humidity regulator, a NO sensor, the solenoid valve VI or the solenoid valve VII; a normally open end of the tee valve I is connected with the front of the air chamber I or the air chamber II and with the analysis pump, and a passage switching end of the tee valve I is connected with the front of the air chamber I or the air chamber II and with a NO filter and the analysis pump; and a normally open end of the tee valve II is connected with the analysis pump, the air humidity regulator and the NO sensor, and a passage switching end of the tee valve II is connected with the analysis pump, a CO sensor and a CO filter.