Cellulose nanofiber (CNF) is a lightweight, high strength material with outstanding functions such as a high gas barrier property, absorption, and transparency. Because CNF is plant-derived, it is also a low environmental impact material in production and waste disposal processes. Measurement of the degree of crystallinity is one method for evaluation of the main characteristics that influence the chemical and physical properties of cellulose. For example, strength tends to increase with the degree of crystallinity. This application news introduces an example of measurement of the degree of crystallinity of CNF by X-ray diffraction.