To provide a method effectively synthesizing and purifying a derivative of 6-nitroindoline useful as raw material for an intermediate of a medicine, an agrochemical and an intermediate for a compound for an electronic material.

This method prepares 6-nitroindoline derivative (formula 2) (R1 is H or a protecting group for an amino group, R2 and R3 are each H or an alkyl group.) by feeding air to an indoline derivative (formula 1) (R1, R2 and R3 are each has same meaning as above described.) and then reacting a reagent having nitrating capability under a condition promoting protonation of the N atom in the indoline derivative to position selectively obtain the derivative.