Provides a solid oxide fuel cell with which product life can be extended while a practical output power is maintained. The present invention is a solid oxide fuel cell, having a fuel cell module (2), a fuel supply device (38), an oxidant gas supply device (45), and a controller (110) for controlling the fuel supply amount; whereby the controller is furnished with a degradation determining circuit (110a) for determining degradation in a fuel cell module, and with a fuel correction circuit (110b) for correcting operating conditions based on a degradation determination; the fuel correction circuit can execute an increasing correction mode for increasing the fuel supply amount supplied to the fuel cell module so that rated output power is maintained, or can execute a decreasing correction mode for reducing rated output voltage so that the fuel supply amount is reduced; there is also a mode selection device (110c) for selecting correction modes.