PURPOSE: To obtain the high-purity titled compound by one step, by reacting an inexpensive aniline with ethylene glycol as raw materials in a gas phase in the presence of a catalyst selected from the group consisting of cadmium phosphate, zinc phosphate, aluminum phosphate, boron phosphate, and silver.

CONSTITUTION: In the presence of one or more catalysts selected from the group consisting of cadmium phosphate, zinc phosphate, aluminum phosphate, boron phosphate, and silver, 1mol of an aniline (e.g., aniline, p-toluidine, etc.) is reacted with 0.05W2mol ethylene glycol at 250W400°C in a gas phase to give indole or its derivative (e.g., 5-methylindole, etc.).

EFFECT: A very small amount of by-products occurs, and the selectivity is superior.

USE: A raw material for synthesizing spice and an amino acid.