A first time series data includes a plurality of element sets each including numeric data and text data. A numeric key concept of the numeric data is extracted from each element set of the first time series data. A text key concept of the text data is extracted from each element set of the first time series data. A second time series data corresponding to the first time series data is generated. In the second time series data, each element set includes the numeric key concept and the text key concept. A support of at least one combination of each numeric key concept and each text key concept is calculated from the plurality of element sets of the second time series data. The support is a degree belonging to the numeric key concept or the text key concept. A frequent time series pattern is extracted from the second time series data by referring to the support.