Abstract: An apparatus for collecting samples by gel electrophoresis has a base table, a cutting tool or an extractor disposed above the base table, a moving mechanism, a pattern detector and a control device. The base table is for placing thereon a gel in the form of a slab with one of its sandwiching support plates removed therefrom in such a way that the gel is exposed in the upward direction. The cutter is for cutting out a specified portion of the gel, and the extractor is for extracting a specified migration band in such a specified portion of the gel by electrophoresis. The moving mechanism is for moving the cutter, or the extractor, three-dimensionally. The pattern detector is for optically detecting migration patterns in the gel on the base table so as to enable the user to determine which part of the gel or which migration band thereon is of interest.