A method of precisely measuring the track twist of a track on which a vehicle for commercial operation is travelling using this vehicle is to be provided. A method in an embodiment of the present invention is a method of measuring a condition of a track (R) on which a vehicle for commercial operation (100) is travelling using this vehicle (100). The vehicle for commercial operation includes a bogie (10). The bogie includes four wheels (1) and primary springs (2) provided to correspond to the four wheels (1) and support the corresponding wheels (1), and is capable of measuring a wheel load of each of the four wheels (1). The method includes the steps of: measuring the wheel load of each wheel (1) (S13); calculating the displacement of each primary spring (2) based on the measured wheel load (S15); and calculating the track twist (h) of the track (R) based on the calculated displacements of the primary springs (2) (S18).