The problem of the present invention is provision of a crystal of (2R,4R)-monatin salt superior in sweetness, which is superior in preservation stability, solubility and coloring stability. The crystal of (2R,4R)-monatin potassium salt of the present invention shows an X-ray powder diffraction pattern having characteristic peaks at diffraction angles 2θ of 5.5°, 7.2°, 8.1°, 8.9° and 16.3°, by powder X-ray diffraction (Cu-Kα radiation).