An excrement collection device includes a casing having a bottom wall, two opposing first outer sidewalls, and a second outer sidewall connecting the first outer sidewalls; a receiving space defined by the bottom wall, the first outer sidewalls, and the second outer sidewall and divided into a temporary storage region and a collection region, with the temporary storage region disposed between the second outer sidewall and the collection region; a cleansing component disposed in the temporary storage region; and a support component disposed at the top of the temporary storage region and having rotatable support boards. Excrement left behind at home by pets because of defecation and urination is gathered in the collection region to thereby spare pet keepers the hassles of frequent cleansing, prevent exposure of the excrement to air for a long period of time, and preclude a foul-smelling odor otherwise lingering at home.