PURPOSE: To make it possible to perform highly generalized control by analyzing a bit pattern of data stored in variables by means of a program reading means and discrimination means of a control device thereby branching conditions of an NC program.

CONSTITUTION: At first an NC program is read block by block by means of a program reading means 71. Based on the output from the reading means, presence or absence of a specified NC command is discriminated by means of a program discrimination means 72. If present, the signal is sent to a data reading means 73 where a variable number at which a data specified by a user is stored, a bit position to be searched, and a sequence number to which branching is addressed are red. Then a bit discrimination means 74 searches variable data for the presence of a bit and, if a bit of a specified position is present, reading of a next program is continued by a 2nd program reading means 75. If not present, process is branched via a data branching means 76 to a block of a set sequence number. Thus, conditions of an NC program can be branched by means of external and internal input signals, etc.