Disclosed is an abnormal pattern detection program for a function call in a source program that makes a computer, which is connected to a main memory and an output device, execute the following processes. (1) A reading process for reading the source program onto the main memory. (2) A sentence extracting process for extracting previous and next sentences of every function call of each function from the source program read onto the main memory. (3) A setting process for setting common appearance patterns, which are included in the previous and next sentences of every function call extracted through the sentence extracting process and appear in a high frequency, on the main memory. (4) An output process for outputting a warning message from the output device when a function call whose previous and next sentences do not include any of the common appearance patterns is found in the source program.