To provide an intake parameter-calculating device and intake parameter-calculating method for an internal combustion engine, which are capable of accurately calculating intake parameters in a case where an intake throttle valve is provided. The intake parameter-calculating device 1 includes an ECU 2. The ECU 2 calculates an error KTHERRCOR using an error model equation (8) (step 2), and calculates a correction coefficient KTHCOR as the reciprocal of the sum of the error KTHERRCOR and 1 (step 3). The ECU 2 calculates a passing air amount GAIRTH by correcting a basic passing air amount GAIRTHN calculated by an equation (11) using a correction coefficient KTHCOR (step 6). A model parameter A for the error model equation (8) is calculated using equations (14) to (18) by onboard identifying calculation with uniform weighting (steps 48 to 53).