In this study, a ZnO/diamond structure ultraviolet (UV) photodetector was fabricated and investigated. ZnO films with thickness of 50 and 100 nm were deposited on half of diamond substrates by sputtering technique. Then, electrodes were patterned on ZnO and diamond areas to form photodetectors. The photocurrent gain in the UV region has been strongly influenced by ZnO film. ZnO films with thickness of 50 and 100 nm on diamond substrates reaches 14.3 and 308 A/W, respectively. Both of peak responsivities were located at 270 nm. Additionally, two shoulder peaks around 240 nm and 290 nm were observed for ZnO/diamond photodetector, which may stem from diamond and ZnO, respectively.