To provide a method for accurately and quickly measuring the amount of bonding of ketone in liquid crystalline polymer.

For a plurality of the liquid crystalline polymers having a known amount of bonding of ketone, a near infrared ray spectrum having a wavelength of 600 to 2500 nm is obtained, the relationship between the amount of bonding of ketone and near infrared ray spectrum is obtained by the analysis method using the partial least square regression analysis, and the amount of bonding of ketone in the crystal polymer is estimated according to the near infrared ray spectrum of the liquid crystalline polymer having an unknown amount of bonding of ketone.