A log acquisition method is provided that allows a processing log of software to readily be acquired and reduces the man-hours needed for analyzing a bug. The log acquisition method is a method for acquiring a runtime log of a program 91 including a function (FuncAA), comprising the step of changing the address of the function (FuncAA) loaded to the address of a function (92) for log acquisition, wherein the function (92) for log acquisition comprises the steps of: calling the function (FuncAA) (96) to cause a predetermined process to be executed (97), receiving the result of the execution (98), and passing said result to said program 91 (101), recording given information when calling the address of the function (FuncAA) (95, 100), and recording given information when receiving the result of the execution (99, 100).