Provided is a novel process for producing a (2S)-2-[(1H-pyrazol-1-yl)methyl]-1,3-oxazinane derivative.More specifically, provided is a process for producing a (2S)-2-[(1H- pyrazol-1-yl)methyl]-1,3-oxazinane derivative represented by formula (1):the process comprising reacting 3-aminopropan-1-ol with glyoxylic acid.