The invention provides a granular anionic surfactant and a detergent composition blended with the same. Disclosed are a process for producing a granular anionic surfactant, which including stirring particles containing 50 to 100 wt % of an anionic surfactant at a temperature at which the anionic surfactant exhibits thermoplasticity at a stirring Froude number as defined below by equation (i) of 0.1 or more and less than 2.0; a granular anionic surfactant obtained by the process; a granular anionic surfactant having a surface roughness (Ra) of 1.0 μm or less; and a detergent composition comprising the granular anionic surfactant. Fr=V/[(R×g)0.5]  (i) wherein Fr is Froude number, V is the peripheral speed at the top of a stirring blade [m/s], R is the radius of gyration of a stirring blade [m], and g is the acceleration of gravity [m/s2].