A bendable water-cooling device includes: a pump unit having a pump case and a driver. The pump case has a pump chamber, a first inlet and a first outlet. The pump case is formed with a first pivotal connection section on the same side as the first outlet; a heat exchange unit having a liquid reservoir case and a heat dissipation member, the liquid reservoir case having a heat exchange chamber, a second inlet and a second outlet, the liquid reservoir case being formed with a second pivotal connection section on the same side as the second inlet; and a pivot unit having a first mating section and a second mating section respectively pivotally connected with the first and second pivotal connection sections. The pump unit and the heat exchange unit are bendable around the pivot unit from a horizontal position to an upper and lower overlapping position.