Slush fluid such as slush hydrogen and slush nitrogen is a two-phase (solid-liquid) single-component cryogenic fluid containing solid particles in liquid, and consequently its density and refrigerant capacity are greater than for liquid state fluid. Experimental tests were performed with slush nitrogen to obtain the frictional pressure drop flowing in a 15 mm internal diameter, 400 mm long, horizontal, stainless steel pipe. The primary objective of this study was to investigate the pressure drop reduction phenomenon with changes in velocity and solid fraction. From the experimental results, the pressure drop correlation between the friction factor and the Reynolds number was obtained and an empirical correlation was derived. Flow patterns for slush nitrogen inside a pipe and the behavior of solid particles were also observed using a high speed camera.