To provide a method for producing propionaldehyde directly from glycerol with high yield, gasified glycerol is brought into contact with a silica-type regular mesoporous body. More specifically, gasified glycerol is supplied to a catalyst layer containing a regular mesoporous body while heating the catalyst layer at a temperature ranging from 200 to 800° C. in such a manner that a W/F value can fall within the range from 0.001 to 1000 g·min/ml inclusive wherein W represents an amount (g) of a catalyst and F represents a supply rate (ml/min) of supplied glycerol.