To provide a fiberboard capable of reducing a load on the environment at all states of producing, using, and abolishing and moreover having a high degree of bending strength and a high bending-strength retention rate at high temperature and high humidity so as to be usable for an automobile interior material or building material and a fiber-board producing method. The fiberboard is formed by mixing natural fiber with polylactic acid resin serving as a binder and has an apparent density of 0.2 g/cm3.