To provide a collection device capable of efficiently collecting useful metals such as uranium, vanadium, cobalt and titanium dissolved in micro amount in sea water in which a collection material having amidoxime group to collect the metals from sea water with high efficiency is used.

A floating type collection device is moored in a sea while suspending an adsorption floor unit filled with collection materials from a bottom part of a floating type artificial land afloat on the sea. In a pier type collection device, the adsorption floor unit is suspended between piers of a bridge to connect islands to each other or an island to a cape. In a long-line collection device, the adsorption floor unit is suspended from a rope extended in the sea, and in a floating body type collection device, the adsorption floor unit is suspended in the sea from a floating type pool.