<p>Core debris generated during a molten reactor core in a reactor containment vessel penetrating the reactor containment vessel is configured to be caught by a core catcher located beneath the reactor containment vessel which has a main body (20) having first stage cooling water channels (21 a) and second stage (21 b) surrounded by cooling fins (31) extending radially. The number of the second stage cooling channels (21 b) is larger than that of the first stage cooling channels (21a). Cooling water is supplied from a cooling water injection opening (22) and distributed to the first cooling water channels (21 a) at a distributor (10). An intermediate header (21) is formed between the first and the second cooling water channels (21 a, 21 b), and the cooling water is distributed to the second cooling water channels (21 b) uniformly.</p>
