A machine control device includes: a diagnostic test time calculation unit that calculates a scheduled execution time of a diagnostic test; a program execution time prediction unit that predicts a predicted ending time of a program before executing the program; a diagnostic test execution determination unit that determines whether to execute the diagnostic test at a predetermined time, by determining whether the predicted ending time of the program exceeds the scheduled execution time of the diagnostic test, and a diagnostic test execution unit that executes the diagnostic test, in which, in a case in which the predicted ending time of the program exceeds the scheduled execution time of the diagnostic test, the diagnostic test execution determination unit instructs the diagnostic test execution unit to execute the diagnostic test prior to the scheduled execution time of the diagnostic test before executing the program.