To improve a method for checking a splicing device, and to make the check during the operation for production possible.

A pneumatic splicing device has splicing chambers respectively connected to a compressed air source through each conduit, and the conduit has a solenoid splicing valve connected to a control unit for sending the opening/ closing signal. With this structure, at the time of splicing process, the pressure forming condition to be generated between the splicing chamber 10 and the splicing valve 11 is detected in the conduit 15 after the opening signal is sent, and the pressure value is compared with the reference value, and in the case where a deviation between the reference value and the measurement value exceeds the predetermined value, the error signal is triggered.