Provided an apparatus configured to calculate a periodicity of time series data, generate a plurality of subsequences, from the time series data, a length of each subsequence set to the periodicity, calculate feature values of the plurality of subsequences; categorize the plurality of subsequences, based on the feature values thereof, into one or more groups, find a periodicity of the subsequences belonging in common to one group, based on an occurrence order of the subsequences belonging in common to the one group and perform missing event detection by identifying the subsequence, occurrence of which is expected according to the periodicity of the subsequences belonging in common to the one group, but not found.