This paper presents a cell stretching microdevice for in-situ observation of stretched cell. In a conventional cell stretching device, it was difficult to observe the initial and in-situ cellular response to stretching. The presented device consists of an elastic culture chamber and leaf springs by which uniaxial stretch is applied to the culture chamber. The device is produced by a micro three-dimensional structure fabrication process using multiple exposures to the photoresist. The device permits the observation of cellular responses to stretching in real time because it is made of transparent materials when observed by optical microscope. We demonstrated the fundamental characteristics of a microdevice, and observed the cellular response behavior by a fabricated microdevice. The amount of the culture chamber deformation was controlled by the amount of the stretching arm displacement. Also, we demonstrated the culture chamber during stretching was not deformed toward the optical axis. Moreover, in-situ observation of transition of the cellular calcium signaling response to stretching succeeded by optical microscopy using fabricated microdevice. These results indicated that this device can be used to observe and evaluate the initial cellular response and micro-strain field on a cell membrane during uniaxial stretching.