We present an experimental system for real-time monitoring of 3D constructed tissues at single-cell resolution to further understand cellular response against mechanical stimuli. The system enables us to continuously monitor the same cells in a 3D tissue at a subcellular level under uniaxial cyclic stretch. We confirmed our system's effectiveness by observing that 3D tissues cultured under cyclic stretch were oriented to the direction of stretch. Moreover, cells in a 3D tissue were successfully observed continuously at single-cell resolution even under cyclic stretch. We believe that the real-time observation of cellular response against mechanical stimuli with our demonstrated system could be an effective method for investigating the relationship between cellular response and mechanical stimuli in detail.