To provide a method for synthesizing and purifying a 6-substituted indole derivative useful as an intermediate for medicaments/agrochemicals and electronic material compounds.

This method for producing a 6-substituted indole derivative of formula 3(R1 is H or a protective group for amino group; R2 and R3 are each H or an alkyl; and R4 is amino or nitro) is characterized by comprising the following process: an indoline derivative of formula 1 (R1, R2 and R3 are the same as described above) is reacted with a reagent having nitration ability in the presence of a polymerization inhibitor under such conditions as to promote the protonation of the N-atom in the indoline derivative to form the corresponding 6-nitroindoline derivative of formula 2 (wherein, R1, R2 and R3 are the same as described above) in a site-selective way, which is then put to dehydrogenating reduction.