The present invention provides a crystal of a europium compound containing europium. The present invention enables the preparation of a crystal of a europium compound having a powder X-ray diffraction pattern having a first diffraction peak in diffraction angle (2θ) range of 34.3° to 36.1° in which a half width of the first diffraction peak is 1.8° or less, and/or having a second diffraction peak in diffraction angle (2θ) range of 28.6° to 29.6° and a third diffraction peak in diffraction angle (2θ) range of 36.8° to 38.4° in which a half width of the second diffraction peak is 1.0° or less and a half width of the third diffraction peak is 1.6° or less, and being at least one compound selected from compounds represented by formulae (1) to (4): EuClx  (1) Eu(OH)2  (2) Eu(OH)2Cl  (3) EuOCl  (4) x is 0.05 or more and 5 or less.