Provided is a dual-purpose blackboard device. The dual-purpose blackboard device comprises a frame and a blackboard body which is made of transparent glass and fixedly connected with the frame. A holographic transparent projection film is pasted on the back face of the blackboard body. A row of triangular prisms which can rotate synchronously are arranged on the rear portion of the blackboard body, the side surfaces of all the triangular prisms are consistent relative to the arranged position of the blackboard body, and the side surface of each triangular prism is provided with a plastic cement colored paper layer. The dual-purpose blackboard device mainly has the advantages that the blackboard body is made of transparent tempered glass, a gel ink pen or an oily pen is used for writing on a blackboard, and thus the dust pollution problem caused by chalk is completely solved; due to the fact that the holographic transparent projection film is pasted on the back face of the blackboard body, projection content can be directly displayed on the blackboard; for the reason that the row of triangular prisms which can rotate synchronously are arranged on the rear portion of the blackboard body, all the triangular prisms form the background of the blackboard body through the plastic cement colored paper layers arranged on the side surfaces of the triangular prisms, background colors can be chosen according to teaching content, and the colors of the plastic cement colored paper layers can also be replaced conveniently; due to a blackboard eraser tool, the blackboard can be wiped clean quickly and conveniently.