This paper deals with the results of comparative experiments carried out with models having several different shapes and sizes of the marine suction bell-mouth and simple strainer for the purpose of examining the head-loss of the bell-mouth and the strainer. The following points were made clear as this experiments. (1) The loss coefficient of bell-mouth, at the range higher than about 1.0 × 10⁵ Reynolds number, attains a fixed value unrelated to Reynolds number, and its absolute value is not much affected by variation in the shape of the open mouth part or in the curvature radius. (2) However, it is greatly affected by the amount of clearance between the open mouth part of bell-mouth and the bottom of tank. (3) As regards the strainer, it was confirmed that its loss coefficient also attains a fixed value unrelated to Reynolds number, but that its absolute value changes in accordance with the ratio of clear of the rose plate.