A mounting order determination device configured to determine a mounting order of multiple electronic components (PA to PD) divided into multiple groups prior to mounting work of mounting multiple electronic components (PA to PD) at respective mounting positions on a board (K, KA, KB, KC) by using a component mounting machine (1, 11, 12) or a component mounting line configured by arranging multiple component mounting machines (1, 11, 12) in a row, the mounting order determination device comprising: a level setting section configured to set level information, in which mounting order priorities are ranked, for each component type, the target of which being of at least one of a multilayer mounting component type group that includes a component type of multiple electronic components (PA to PD) having a possibility of being mounted in an up-down direction in layers, and a close-proximity mounting component type group that includes a component type of multiple electronic components (PA to PD) for which the mounting order is restricted due to having a possibility of a large-sized component having a large height dimension being mounted before a small-sized component having a small height dimension being mounted in close proximity thereafter, such that the mounted large-sized component interferes and thereby hinders the mounting work; characterized by further comprising: a component extracting section configured to extract a combination of multiple electronic components (PA to PD) from a group out of the multiple groups of components, the combination to which at least one of multilayer mounting and close-proximity mounting is applied, based on dimensions and mounting positions of the multiple electronic components (PA to PD); and an order determination section configured to determine the mounting order of the electronic components (PA to PD) in the combination based on the layer information set for the component types of the electronic components (PA to PD) included in the combination. a level setting section configured to set level information, in which mounting order priorities are ranked, for each component type, the target of which being of at least one of a multilayer mounting component type group that includes a component type of multiple electronic components (PA to PD) having a possibility of being mounted in an up-down direction in layers, and a close-proximity mounting component type group that includes a component type of multiple electronic components (PA to PD) for which the mounting order is restricted due to having a possibility of a large-sized component having a large height dimension being mounted before a small-sized component having a small height dimension being mounted in close proximity thereafter, such that the mounted large-sized component interferes and thereby hinders the mounting work; characterized by further comprising: a component extracting section configured to extract a combination of multiple electronic components (PA to PD) from a group out of the multiple groups of components, the combination to which at least one of multilayer mounting and close-proximity mounting is applied, based on dimensions and mounting positions of the multiple electronic components (PA to PD); and an order determination section configured to determine the mounting order of the electronic components (PA to PD) in the combination based on the layer information set for the component types of the electronic components (PA to PD) included in the combination. a component extracting section configured to extract a combination of multiple electronic components (PA to PD) from a group out of the multiple groups of components, the combination to which at least one of multilayer mounting and close-proximity mounting is applied, based on dimensions and mounting positions of the multiple electronic components (PA to PD); and an order determination section configured to determine the mounting order of the electronic components (PA to PD) in the combination based on the layer information set for the component types of the electronic components (PA to PD) included in the combination.