1. A fault analysis apparatus comprising: a log element extraction unit configured to extract, from one or more pieces of log information which are output by an information processing system, a log element which is an element constituting the log information; a log combined unit configured to attach, to each of the log elements, system constituent element information expressing a system constituent element related to the log element, the system constituent element being a constituent element of the information processing system, and generate combined log information by combining the log elements attached with the system constituent element information; a pattern extraction unit configured to extract a pattern of information including the system constituent element information from the combined log information; a pattern conversion unit using an analysis target pattern, being the pattern extracted during an analysis target period in which an analysis is performed, and when the analysis target pattern includes system constituent element information of a conversion target which is system constituent element information not included in a comparison target pattern being a pattern stored in a pattern storage unit and being the pattern extracted during a comparison target period which is a period when a conversion is performed, configured to perform the conversion between the system constituent element information of the conversion target and the system constituent element information included in the comparison target pattern and similar to the system constituent element information of the conversion target in any one of the comparison target pattern and the analysis target pattern; a pattern comparison unit configured to detect a difference by comparing the analysis target pattern and the comparison target pattern after conversion processing with the pattern conversion unit; and a cause portion presenting unit configured to present, as a portion of a cause of a fault, the system constituent element information indicated by the difference detected by the pattern comparison unit.