This paper describes the introductive guide for a laser diffraction particle size analyzer（SALD-3000S； Shimazu Co., Ltd．），and discuss the comparison of data obtained from different analytical methods and analyzers．SALD-3000S is abailable for any sand and mud material，and its measurement range covers from 0.08 to 3000μm．SALD-3000S has several advantages such as simple suitability of a laser axis，and real-time modulation of sample bulk concentration，in comparison with previous laser diffraction particle size analyzers．Measurements of well-known diameter samples coincide with true values of diameter．Measurements of sand-mud samples with three different grain analyzers of a settling-tube grain sizer，the previous laser diffraction particle size analyzer（measurement range：0.1-192μm），and SALD-3000S，suggests that SALD-3000S provides the most precise and is the simplest to measure．