A honeycomb structural body includes at least one honeycomb unit which has a longitudinal direction. The at least one honeycomb unit includes plural cell walls, an inorganic binder, and inorganic particles. The plural cell walls extends along the longitudinal direction from one end face to another end face of the at least one honeycomb unit to define plural cells. The inorganic particles include ceria particles, and a ceramic material which has a degree of self-sintering lower than a degree of self-sintering of the ceria particles.