The present invention provides a novel process for producing an N-substituted aziridine compound by subjecting an N-substituted alkanolamine to a gas-phase catalytic dehydration reaction (the following reaction formula). ##STR1## In the above formula, R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are each independently one member of selected from a hydrogen atom and alkyl groups of 1-4 carbon atoms, and X is one member selected from alkyl groups of 1-4 carbon atoms, a cyclohexyl group, a phenyl group, a benzyl group, hydroxyalkyl groups of 1-4 carbon atoms and aminoalkyl groups of 1-4 carbon atoms. Preferably, the N-substituted aziridine compound is produced at a high yield by subjecting an N-substituted alkanolamine to a gas-phase catalytic dehydration reaction in the presence of a silicon-containing or phosphorus-containing catalyst under the conditions of reaction pressure=5-250 mmHg, reaction temperature=300.degree.-450.degree. C. and space velocity=50-500 hr.sup.-1 (STP).
