The invention discloses a safe advertising device. The device comprises a preset groove formed in the building wall and an advertising board, an advertising board groove is formed in a notch in the upper portion of the preset groove, inserting and connecting grooves extending downwards are oppositely formed in the left end and the right end of the advertising board groove, a locking groove is formed in the end face of the inner side of each inserting and connecting groove, a pushing groove communicated with the preset groove is formed in the end face of the inner side of each locking groove, and a fixed hole tube is arranged in the portion, between the two pushing grooves, of the preset groove. Accordingly, by means of cooperation of an inserting and connecting block and a first elastic part, the advertising board is firmly locked in the advertising board groove, automatic locking and connecting after advertising board installation are achieved, advertisement fixing is safe and firm, and operation is easy.