Introduction: Nowadays, a resistive switching memory using biological, transparent, and environmentally friendly materials is appreciated as the tendency of science and technology, especially in the field of electronic devices. Chitosan (CS), having dominant characteristics such as non-toxic, biocompatible and large capacity, plays as a switching medium in resistive random access memory devices (RRAM). Methods: In our study, CS film was fabricated onto a commercial substrate (FTO) using a simple spin coating method, and the top electrode (Ag) was deposited by a direct-current sputtering technique. Results: The Ag/CS/FTO devices shown the bipolar switching behavior when applying sequence voltage from -1.5 to 2V with the set process in the negative bias and the reset process in the positive bias. The content (0.2, 0.5, and 0.8 wt%) and thickness (100, 300, 500 nm) of chitosan film significantly affect the resistive switching performance. The devices with 0.5 wt%/v concentration and 300 nm-thickness of CS have shown better efficiency than the others with endurance over 100 sweeping cycles and ON/OFF ratio at ca. 2x10 times. Conclusions: It is found that the chitosan material has a large potential candidate for applications in optoelectronic devices.