Cell motility is one of the most attractive phenomena among cell activities, and variety types of motility are observed in protozoa. I have studied on the mechanism of amoeboid movement, employing glycerinated model, reconstitution model, analysis of membrane dynamics and compression model. The data demonstrates that the dominant motive force of the movement is the hydrostatic pressure which was generated by the contraction of actomyosin layer in the subcortical cytoplasm. The plasma membrane is pushed by the pressure and extends forward by unfolding the wrinkles of the cell surface at the rear region. The smooth extension of the plasma membrane is achieved by its high fluidity.