An analysis apparatus comprising: a model generation unit configured to collect a structure model and operation information of each device of an existing plant and to generate an entire variation model comprising plurality of partial variation models, wherein the operation information is an information obtained by measuring an actual operation result of each device of the existing plant; a variation model storage unit configured to store the plurality of partial variation models indicating variation in characteristics of the existing plant corresponding to an operating condition of the existing plant, wherein the variation model storage unit is configured to store each of the plurality of partial variation models in a block unit including one or more devices in the existing plant, and the variation model storage unit is configured to store each of the plurality of partial variation models and a structure of the block unit in association with each other; a a model extraction unit configured to acquire structure information indicating a structure model of an existing analysis target plant and to extract partial variation models for each block unit included in the structure model of the existing analysis target plant corresponding to the structure information; wherein the model extraction unit is configured to extract the partial variation models, which corresponds to a target block units included in the structure model of the existing analysis target plant, from the variation model storage unit, and the model extraction unit is configured to extract the partial variation models corresponding to the target block units, based on a degree of similarity between a structure of the respective target block unit and a structure of the block unit corresponding to the respective partial variation model; an analysis unit configured to output an analysis result indicating an operation of the existing analysis target plant in the future, based on the structure model of the existing analysis target plant and the partial variation models extracted by the model extraction unit. 2. a model generation unit configured to collect a structure model and operation information of each device of an existing plant and to generate an entire variation model comprising plurality of partial variation models, wherein the operation information is an information obtained by measuring an actual operation result of each device of the existing plant; a variation model storage unit configured to store the plurality of partial variation models indicating variation in characteristics of the existing plant corresponding to an operating condition of the existing plant, wherein the variation model storage unit is configured to store each of the plurality of partial variation models in a block unit including one or more devices in the existing plant, and the variation model storage unit is configured to store each of the plurality of partial variation models and a structure of the block unit in association with each other; a a model extraction unit configured to acquire structure information indicating a structure model of an existing analysis target plant and to extract partial variation models for each block unit included in the structure model of the existing analysis target plant corresponding to the structure information; wherein the model extraction unit is configured to extract the partial variation models, which corresponds to a target block units included in the structure model of the existing analysis target plant, from the variation model storage unit, and the model extraction unit is configured to extract the partial variation models corresponding to the target block units, based on a degree of similarity between a structure of the respective target block unit and a structure of the block unit corresponding to the respective partial variation model; an analysis unit configured to output an analysis result indicating an operation of the existing analysis target plant in the future, based on the structure model of the existing analysis target plant and the partial variation models extracted by the model extraction unit. 2.