In this paper, we propose an instantaneous phase-stepping method for determining phase distribution of interference fringes utilizing a camera that is equipped with a micro-polarizer array on the sensor plane. An optical setup of polarization interferometry using a Mach–Zehnder interferometer with two polarizers is constructed. Light emerging from the interferometer is recorded using a camera that has a micro-polarizer array. This micro-polarizer array has four different optical axes. That is, an image obtained by the camera contains four types of information corresponding to four different optical axes of the polarizer. The four images separated from the image recorded by the camera are reconstructed using gray level interpolation. Subsequently, the distributions of the Stokes parameters that represent the state of polarization are calculated from the four images. The phase distribution of the interference fringe pattern produced by the Mach–Zehnder interferometer is then obtained from these Stokes parameters.The effectiveness of the proposed method is demonstrated by measuring a static carrier pattern and time-variant fringe patterns. It is emphasized that this method is applicable to time-variant phenomena because multiple exposures are unnecessary for sufficient data acquisition in the completion of the phase analysis. In this paper, we propose an instantaneous phase-stepping method for determining phase distribution of interference fringes utilizing a camera that is equipped with a micro-polarizer array on the sensor plane. An optical setup of polarization interferometry using a Mach-Zehnder interferometer with two polarizers is constructed. Light emerging from the interferometer is recorded using a camera that has a micro-polarizer array. This micro-polarizer array has four different optical axes. That is, an image obtained by the camera contains four types of information corresponding to four different optical axes of the polarizer. The four images separated from the image recorded by the camera are reconstructed using gray level interpolation. The distributions of the Stokes parameters that represent the state of polarization are calculated from the four images. The phase distribution of the interference fringe pattern produced by the Mach-Zehnder interferometer is then obtained from these Stokes parameters. the effectiveness of the proposed method is demonstrated by measuring a static carrier pattern and time-variant fringe patterns. It is emphasized that this method is applicable to time-variant phenomena due to multiple exposures are unnecessary for sufficient data acquisition in the completion of the phase analysis