An installation device of an advertisement board comprises a fixed frame which is firmly installed in a wall body and an installation arm which is firmly connected to the rear end of the advertisement board, wherein a limiting groove is formed in the upper end face of the installation arm; an installation groove which has a forward opening and is used to install the installation arm is formed in the fixed frame; a vertical telescopic groove is formed in the upper end wall of the fixed frame; a limiting pin fitted with the limiting groove is installed in the vertical telescopic groove in a sliding manner; an ejection pressing plate is firmly installed on the upper end of the limiting pin; and an ejection pressing spring which ejects and presses the limiting pin into the limiting groove is installed on the upper end of the ejection pressing plate. During installation of the advertisement board, only the installation arm needs to be pushed into the installation groove; when the limiting pin is inserted into the limiting groove, the installation arm will be limited in a single direction and cannot be plugged out. At this moment, installation of the advertisement board is completed. The installation course is simple and convenient; installation is stable; the advertisement board does not fall easily; and thus hidden safety dangers are reduced.