The present invention relates to a method for easily producing a tertiary amine with high yield. A tertiary amine represented by general formula (1) is produced by adding a metal-containing reagent represented by general formula (6) into a reaction system consisting of thioamide represented by general formula (4), a methylating agent represented by general formula (5) and a solvent, and then adding thereto a Grignard reagent represented by general formula (7).
1
CH
3
—X (5)
R
8
-M
1
(6)
R
7
-M
2
(7)