PURPOSE: To make an apparatus short and to make a packaging speed fast by a method wherein a bag-packaged product is delivered to a horizontal bar from a horizontal belt conveyance device capable of being tilted, raised and lowered freely and its weight is weighed accurately and quickly without an interference by the vibration of a belt.

CONSTITUTION: A bag-packaged product W is sandwiched between a vertical-face guide 1 and a brush roll 2, dropped to, and guided by, a tilted belt 3, and delivered to a horizontal conveyance device 4 capable of being tilted, raised and lowered freely. A belt conveyance face 4a is raised to be. higher than a horizontal bar 5c, and the packaged product W is received on the bar 5c and transferred up to a stopper 12. At this time, the stopper 12 issues a detection signal, and a CPU 6 to which the signal has been input reduces an air cylinder device 4e, lowers and tilts a horizontal belt 4 and delivers the packaged product W onto the bar 5c. A load cell 5a weighs the packaged product W in a stationary state, and the CPU 6 computes its weight, compares the weight with a threshold value. The packaged product W within a permissible range is carried out by a carrying-out belt 10 by raising the horizontal belt 4, and the packaged product W outside the permissible range is discharged.