A log labeling apparatus is configured to include a label importance DB and a similarity DB configured to store importance information between a plurality of labels and an action set and action set information identifying a first action set for calculating a second similarity with each label of a first log unit, a similarity calculation unit configured to calculate the second similarity with each label of the first log unit on the basis of the importance information, an action set of the first log unit, and the action set of the action set information, a post processor configured to detect label candidates, and an accumulation determination unit configured to determine a second action set for calculating a second similarity of a second log unit and to store action set information on the second action set in the similarity DB.