The present invention provides a method by which a 6-hydroxyethyl penam compound represented by General Formula (2) below can be produced with a high selectivity: wherein R represents a hydrogen atom or a protective group for carboxylic acid and X2 represents a halogen atom; the method including the steps of reacting a Grignard reagent with a halogeno penam compound represented by General Formula (1) below: wherein R and X2 are the same as above, and X1 represents a halogen atom; reacting the generated compound with an amine compound; and further reacting the generated compound with acetaldehyde.