A liquid-filled display device includes a hollow member mounted on a transparent top end wall of a hollow base and confining a water-tight inner space filled with a liquid body, and a display unit mounted on the top end wall and having a top wall and two transparent sidewalls connected to the hollow member. The sidewalls and the top wall cooperate with the hollow member and the top end wall to confine a display space. At least one of the sidewalls is provided with an advertisement. An air pump unit is mounted in the base, and is operable so as to supply fine air bubbles into the liquid body through a diffuser set mounted within the inner space. A lamp unit mounted in the base beneath the hollow member is operable so as to radiate colored light that penetrates through the top end wall into the inner space.