A shoe warning light device comprises: a fastening seat having a holding space and disposed in a shoe midsole such that the front wall of the fastening seat is exposed; a luminous body fastened to the front wall of the fastening seat and provided with two polar feet extending into the holding space to form two conducting connections; a housing mounted detachably in the holding space and provided in the top wall thereof with a U-shaped slot forming a flexible tongue; two conducting pieces provided respectively with one end forming a power source connection engageable with one of the two conducting connections, with one of the two conducting pieces extending downwards to locate over the bottom wall of the housing, and with another one of the two conducting pieces extending upwards to locate under the tongue; and a battery disposed in the housing such that it is in contact with one of the two conducting pieces.