An attachment of a hair trimmer comprises a holder and a comb unit. The holder is shaped to be attached to the upper end of the housing. The comb unit is held by the holder. The comb unit has a first comb and a second comb each having a shape different from each other. The comb unit is attached to the holder to be movable between the first position where the first comb is aligned with the cutter and the second position where the second comb is aligned with the cutter. The attachment further comprises the fixing means being configured to fix the comb unit to the holder when the comb unit has the first position. The attachment further comprises the fixing means being configured to fix the comb unit to the holder when the comb unit has the second position.
