A core catcher includes a holding surface that catches and holds corium and that introduces a surrounding coolant into the core catcher and cool the core catcher by heat exchange with the introduced coolant. The holding surface and the cooling unit are constructed by arranging blocks which each include a polyhedron having at least one pair of parallel surfaces and having an opening portion formed in a surface located in a lateral direction when a first surface that is one of the parallel surfaces is arranged as a bottom surface and are configured such that the polyhedrons communicate with each other via the opening portion when the polyhedrons are arranged adjacent in the lateral direction. The core catcher can achieve easier installation of the blocks without an increase in installation cost.