A porous body includes a framework having a three-dimensional network structure, the framework having a body including crystal grains including nickel and cobalt as constituent elements, the cobalt having a proportion in mass of 0.2 or more and 0.8 or less with respect to a total mass of the nickel and the cobalt, the crystal grains having a shorter grain diameter of 2 μm or more, as determined in a first observed image obtained by observing the body of the framework in cross section at a magnification of 200 times.