A machining device comprising a machining device unit and a loading device for loading workpieces into a holder disposed in a first housing of the machining device unit through a first access hole for transfer formed in the first housing, the machining device unit includes the first housing, the first housing includes a first side section in which is formed the first access hole for transfer, the loading device comprising: a second housing having a box-like shape and fixed to the first housing, the second housing and the first housing being juxtaposed with each other; a storage stand having a plurality of vertically disposed hold shelves for storing a plurality of workpieces in such a manner that the workpieces are arranged vertically in the second housing; a transfer device; and an elevator for carrying the transfer device up and down at a side of the storage stand outside the first housing, wherein the second housing includes a second side section in which is formed a second access hole for transfer, the second side section of the second housing is fixed to the first side section of the first housing so that the second access hole for transfer and the first access hole for transfer are connected, the elevator is configured to move the transfer device to a level of a certain workpiece of the plurality of workpieces, the transfer device is configured to pull out the certain workpiece from the storage stand, the elevator is configured to move the transfer device to a level of the first access hole for transfer, wherein the transfer device is configured to load the certain workpiece into the holder through the first access hole for transfer, and each of the hold shelves is configured such that a cassette together with the workpiece held in the cassette can be inserted into the hold shelf and a direction in which a cassette having the workpiece to be fitted therein is inserted into the hold shelf is aligned with a direction in which the cassette is delivered from the second housing to the first housing through the first and second access holes for transfer (12a, 53a). the machining device unit includes the first housing, the first housing includes a first side section in which is formed the first access hole for transfer, the loading device comprising: a second housing having a box-like shape and fixed to the first housing, the second housing and the first housing being juxtaposed with each other; a storage stand having a plurality of vertically disposed hold shelves for storing a plurality of workpieces in such a manner that the workpieces are arranged vertically in the second housing; a transfer device; and an elevator for carrying the transfer device up and down at a side of the storage stand outside the first housing, wherein a second housing having a box-like shape and fixed to the first housing, the second housing and the first housing being juxtaposed with each other; a storage stand having a plurality of vertically disposed hold shelves for storing a plurality of workpieces in such a manner that the workpieces are arranged vertically in the second housing; a transfer device; and an elevator for carrying the transfer device up and down at a side of the storage stand outside the first housing, wherein the second housing includes a second side section in which is formed a second access hole for transfer, the second side section of the second housing is fixed to the first side section of the first housing so that the second access hole for transfer and the first access hole for transfer are connected, the elevator is configured to move the transfer device to a level of a certain workpiece of the plurality of workpieces, the transfer device is configured to pull out the certain workpiece from the storage stand, the elevator is configured to move the transfer device to a level of the first access hole for transfer, wherein the transfer device is configured to load the certain workpiece into the holder through the first access hole for transfer, and each of the hold shelves is configured such that a cassette together with the workpiece held in the cassette can be inserted into the hold shelf and a direction in which a cassette having the workpiece to be fitted therein is inserted into the hold shelf is aligned with a direction in which the cassette is delivered from the second housing to the first housing through the first and second access holes for transfer (12a, 53a).