Snakes are suggested to be predators of early primates. Under evolutional selection pressure by snakes, specific subcortical and cortical areas have evolved to detect threat relevant stimuli, especially snakes in primates (Isbell, 2006). Consistent with the theory, we recently reported that monkey pulvinar neurons responded stronger and faster to snakes than other stimuli (Le et al., 2013). The superior colliculus (SC), which receives inputs from the retina and projects directly to the pulvinar, is one of these areas and plays a crucial role in alerting mechanisms in mammals, especially primates. However, responses of SC neurons to snakes remain unknown in primates. In the present study, we recorded monkey SC neuronal responses to photos of snakes, monkey faces, monkey hands and simple geometrical figures. The monkeys were required to discriminate these 4 categories of the visual stimuli in a delayed non-matching to sample (DMNS) task. Of 983 neurons recorded, 356 neurons were visual responsive. Of these neurons, 43 neurons had their receptive fields at the center of the visual fields, and were located in the antero-lateral part of the SC. Although there were no significant differences in response magnitudes to the 4 categories of the stimuli, they responded faster to the snake images and ratio of snake-best neurons was larger than those of other categories. Multidimentional scaling (MDS) analysis showed that snakes were separated from the other stimuli as early as the first 25 ms period after stimulus onset. These results provide new evidence of SC involvement in rapid snake detection.