A deep-sea video monitoring system on a towed sledge (DVMSTS) was developed to estimate the population density of the snow crab Chionoecetes opilio. Population density of the snow crab was investigated using the DVMSTS in a practical survey. The observations were carried out at 7 survey sites ranging from 200 to 340 m in depth on August 20-29, in 1998. These sites were located off both northern and western Oki Islands in the Sea of Japan. The observations were repeated 8 times and video tapes were recorded for 375 min in total. The observed distances were 15,600 m in total, and the towed DVMSTS was able to sweep the sea bottom over an area of 25,900 m². Sweeping area was obtained by multiplying the observed distance by the width of the DVMSTS (1.66 m). A count of 104 crabs was recorded. Crab densities per 1,000 m² for each observation were estimated to be 1, 3, 3, 3.1, 4.0, 5.6, 6.4 and 10 individuals, respectively. Sex of small crabs less than about 9 cm in carapace width could not be defined from the recorded video images. Because the majority of the crabs did not respond to the light, it was assumed that underwater light hardly affected the crab behavior. The method to estimate the population density of the snow crab using the DVMSTS can be effective, especially for a quantitative survey of the stock abundance of the snow crab.