A numerical controller sequentially reads blocks contained in a machining program, analyzes the read blocks to identify a block that causes an alarm based on mismatch criterion information stored in advance, and generates alarm cause data. The numerical controller then generates, based on the generated alarm cause data, at least one set of proposal patch data for correcting the machining program in such a way that the cause of the alarm is solved and generates a corrected machining program that is the machining program to which the generated proposal patch data is applied.