A liquid pumping apparatus comprising a rotor housing, a rotor having at least one roller, to be rotated by a prime mover, an inner periphery wall of the rotor housing, a flexible tube to be inserted into a gap formed between the rotor and the inner periphery wall and squeezed when the rotor is rotated so as to transfer a liquid fed into the tube, and a deformable guide for guiding the flexible tube in a moving path of the roller. At least one portion of the inner periphery wall is movable so as to approach or separate from the rotor.