An efficient method of boxing fuel injectors with a good yield where a predetermined quality is secured in a predetermined number of fuel injectors forming a set for one engine, that is, a method of boxing fuel injectors, a first number of which are scheduled to be mounted in an engine, in a single box in a second number larger than the first number, provided with a step of measuring a characteristic value for the second number of fuel injectors, wherein when the first number of the characteristic values forms a set, the number of combinations of the characteristic values where a total value of this one sets worth of the characteristic values becomes a first management value or less when selecting one sets worth of the characteristic values from the second number of the characteristic values, is defined as the “number of good part combinations”, and the number of possible combinations of one sets worth of the characteristic values is defined as the “number of possible combinations”, the fuel injectors being boxed in a single box so that the number of the good part combinations becomes a rate of a fourth management value or more to the number of possible combinations.
