Hello Hayashi,
The standard SAP system only parks invoice document if the quantity or the price differs from the purchase order.
If you set in customizing of Logistic Invoice Verification, the parameter in 'EDI Parameters for MM Invoice Verification' for processing on 1 'Unclarified Error: Park Invoice', then the invoices are only parked if there is a variance in price or amount against the PO.
If you want to post invoices via EDI in general, then please refer to modification note 501524.
Hope this information helps.
Best Regards,
Monalisa