A respiratory function testing apparatus capable of testing a respiratory function of a subject more accurately. In the apparatus, a respiratory state detection unit acquires a first signal representative of different inspiratory volumes corresponding to a plurality of breaths of the subject and a second signal representative of intrapleural pressures corresponding to the respective different inspiratory volumes, and detects a plurality of respiratory states corresponding to the different inspiratory volumes and their corresponding intrapleural pressures. A respiratory state determination unit captures a state of the respiratory function of the subject on the basis of the plurality of respiratory states corresponding to the different inspiratory volumes and their corresponding-respective intrapleural pressures.
