A bill validator of master-slave type is provided for easy downloading. A master discriminating circuit (40) is switched from a validating mode to a master mode by operation of the master mode switch (48) to forward the download information to a slave discriminating circuit (40) according to the download programm. The slave discriminating circuit (40) is switched from a validating mode to a slave mode by operation of the slave mode switch (49) so that the download information from the master discriminating circuit (40) is written according to the download program in the writable memory (43) of the slave discriminating circuit (40) via the download output terminal (44) of the master discriminating circuit (40) and the download input terminal (46) of the slave discriminating circuit (40).