The invention relates to a dust collector, a dust cup device and a separating cone of the dust cup device. The separating cone comprises a separating cone body and a reflecting screen, wherein the separating cone body is provided with an inner cavity, an air inlet, an air exhaust outlet and a dust collecting hole, the air inlet is positioned in the peripheral side wall of the top end of the separating cone body, the air exhaust outlet is positioned at the axial top end of the separating cone body, and the dust collecting hole is positioned at the axial bottom end of the separating cone body; the reflecting screen is matched in the inner cavity; and a gap is formed between the reflecting screen and the peripheral side wall of the inner cavity, and the reflecting screen is provided with a plurality of air flow holes. In downward air flow, dust-containing air flow close to the peripheral side wall of the inner cavity moves downwards through the gap between the reflecting screen and the peripheral side wall of the inner cavity; meanwhile, in the air flow moving downwards, dust-free air flow close to the middle of the inner cavity moves upwards through the reflecting of the reflecting screen, and further is exhausted from the air exhaust outlet, then the air flow continuing moving downwards is not influenced, therefore, the phenomenon that the dust in the air flow downwards moving is brought out of the air exhaust outlet by the air flow moving upwards is avoided, thus the air-dust separating effect is improved, and the influences on the service life of a motor and the environment are reduced.