To provide catalyst particles that can exhibit high activity.Catalyst particles, which are alloy particles formed from platinum atoms and non-platinum metal atoms, each alloy particle having a main body that constitutes a granular form; and a plurality of protrusions protruding outward from the outer surface of the main body, in which the main body is formed from a non-platinum metal and platinum, the protrusions are formed from platinum as a main component, and the aspect ratio (diameter/length) of the protrusions is higher than 0 and lower than or equal to 2.