The invention belongs to the field of machines, in particular to an automatic solvent adding device. The automatic solvent adding device comprises a main body, a liquid delivery mechanism and a driving motor, wherein a solvent delivery pipe can be mounted on the main body, the liquid delivery mechanism is used for cyclically squeezing the solvent delivery pipe so as to deliver a solvent, and the driving motor is used for driving the liquid delivery mechanism to cyclically squeeze the solvent delivery pipe. The liquid delivery mechanism is driven by the driving motor to squeeze the solvent delivery pipe so as to achieve quantitative delivery of the solvent, so that the efficiency is high, the ink concentration can be controlled accurately, and a continuous and satisfactory printing effect can be obtained easily.