Plastic pollution is ubiquitously distributed in the marine environment, and the weight of floating plastics have been estimated to more than 200,000 tons. For the past years, various organizations have been conducting recovery operations.In this study, we conducted to clarify the usefulness of a marine debris collection device based on the amount and type of debris collected. The average weekly total weight of the contents collected from the mooring type collection device was 1.2 kg and 1.1 kg at Shonan Port and Yumenoshima Island, respectively. Of this weight, 68% (Shonan Port) and 57% (Yumenoshima) was accounted for by wood chips and other naturally occurring materials. A comparison of the number of artifacts (i.e., plastics) collected on the same day shows that 133 pieces/day (green 36 yellow 4 red 47 blue 39 white 7 pieces) were collected at Shonan Port, while 203 pieces/day were collected at Yumenoshima, indicating a general trend toward more plastics at Yumenoshima. Polypropylene (64%) and polyethylene (16%) accounted for about 80% of the total plastics.