A liquid detection device that is accommodated in a sensor accommodating portion formed in a liquid container containing a liquid therein and detects the liquid in the liquid container using a piezoelectric element, wherein, when a wavelength of a vibration wave to be emitted from the piezoelectric element is λ, a distance H from a rear surface of a vibration wave emitting surface of the piezoelectric element to a wall surface facing the rear surface is represented by Equation 1.
(n×λ/2−λ/4−λ/8)≦H≦(n×λ/2−λ/4+λ/8) (Equation 1)
(where n=1, 2, 3, . . . )