In-flight pressure-sensitive paint (PSP) measurement was performed to visualize the location of a shock wave on an aircraft wing. PSP films were applied to the main wing surface of the Japan Aerospace Exploration Agency (JAXA) Flying-Test-Bed “Hisho”. The aircraft flew at both subsonic and transonic speeds, and the flight altitude was varied between 25,000 feet and 45,000 feet. PSP image acquisition was conducted under trim flight conditions. A PSP lifetime imaging system was developed and loaded onto the cabin of the experimental aircraft. The pulse width of the excitation light source and the image acquisition timing for the two-gate method were determined from the luminescent response of PSP obtained in a calibration chamber. Lifetime images obtained in flight showed that the lifetime-based PSP technique is capable of visualizing shock locations on the actual wing. Shock-foot locations could be clearly observed as the steep change in the gate intensity ratio. At transonic flight speeds, the shock foot moved between the chordwise station of 15-30% depending on flight Mach number and angle of attack.