A method for producing acetic acid, comprising: a carbonylation reaction step of reacting methanol with carbon monoxide in the presence of a catalyst system containing a metal catalyst and methyl iodide, as well as acetic acid, methyl acetate, and water in a reaction vessel to produce acetic acid; an evaporation step of separating a reaction mixture obtained in the carbonylation reaction step into a vapor stream and a residual liquid stream in an evaporator; a lower boiling point component removal step of separating the vapor stream by a first distillation column into a first overhead stream rich in at least one lower boiling point component selected from methyl iodide and acetaldehyde, and a first acetic acid stream rich in acetic acid, and condensing and separating the first overhead stream to obtain an aqueous phase and an organic phase; a first overhead stream recycle step of recycling at least a portion of the aqueous phase and/or organic phase to a reaction vessel; and a crotonaldehyde removal step of separating and removing crotonaldehyde by treating at least another portion of the aqueous phase and/or organic phase by a distillation column; wherein with respect to a reflux ratio of the first distillation column, when only the aqueous phase is refluxed to the first distillation column, a reflux ratio of the aqueous phase is not less than 2, when only the organic phase is refluxed, a reflux ratio of the organic phase is not less than 1, and when both the aqueous phase and the organic phase are refluxed, a total reflux ratio of the aqueous phase and the organic phase is not less than 1.5; and in the crotonaldehyde removal step the distillation column is operated such that at least one of the following conditions (i) to (iii) is satisfied: (i) the reflux ratio of the distillation column is not less than 0.01; (ii) a ratio of a crotonaldehyde concentration (ppm by mass) in a distillate liquid of the distillation column to a crotonaldehyde concentration (ppm by mass) in a charging mixture (former/latter) is less than 1; and (iii) a ratio of a crotonaldehyde concentration (ppm by mass) in a bottom fraction of the distillation column to the crotonaldehyde concentration (ppm by mass) in the charging mixture (former/latter) is more than 1. a carbonylation reaction step of reacting methanol with carbon monoxide in the presence of a catalyst system containing a metal catalyst and methyl iodide, as well as acetic acid, methyl acetate, and water in a reaction vessel to produce acetic acid; an evaporation step of separating a reaction mixture obtained in the carbonylation reaction step into a vapor stream and a residual liquid stream in an evaporator; a lower boiling point component removal step of separating the vapor stream by a first distillation column into a first overhead stream rich in at least one lower boiling point component selected from methyl iodide and acetaldehyde, and a first acetic acid stream rich in acetic acid, and condensing and separating the first overhead stream to obtain an aqueous phase and an organic phase; a first overhead stream recycle step of recycling at least a portion of the aqueous phase and/or organic phase to a reaction vessel; and a crotonaldehyde removal step of separating and removing crotonaldehyde by treating at least another portion of the aqueous phase and/or organic phase by a distillation column; wherein with respect to a reflux ratio of the first distillation column, when only the aqueous phase is refluxed to the first distillation column, a reflux ratio of the aqueous phase is not less than 2, when only the organic phase is refluxed, a reflux ratio of the organic phase is not less than 1, and when both the aqueous phase and the organic phase are refluxed, a total reflux ratio of the aqueous phase and the organic phase is not less than 1.5; and in the crotonaldehyde removal step the distillation column is operated such that at least one of the following conditions (i) to (iii) is satisfied: (i) the reflux ratio of the distillation column is not less than 0.01; (ii) a ratio of a crotonaldehyde concentration (ppm by mass) in a distillate liquid of the distillation column to a crotonaldehyde concentration (ppm by mass) in a charging mixture (former/latter) is less than 1; and (iii) a ratio of a crotonaldehyde concentration (ppm by mass) in a bottom fraction of the distillation column to the crotonaldehyde concentration (ppm by mass) in the charging mixture (former/latter) is more than 1. (i) the reflux ratio of the distillation column is not less than 0.01; (ii) a ratio of a crotonaldehyde concentration (ppm by mass) in a distillate liquid of the distillation column to a crotonaldehyde concentration (ppm by mass) in a charging mixture (former/latter) is less than 1; and (iii) a ratio of a crotonaldehyde concentration (ppm by mass) in a bottom fraction of the distillation column to the crotonaldehyde concentration (ppm by mass) in the charging mixture (former/latter) is more than 1.