To prevent accommodating parts of an upper tray from being fitted in accommodating parts of a lower tray and coming into contact with electronic components accommodated in the accommodating parts of the lower tray and to enable the lower tray to support the upper tray even if the thickness of the tray is thin.

The trays 2 accommodating button cells 1 in corresponding recessed accommodating parts 3 formed in the upper plates 2a of the trays 2 are used by being vertically stacked in a plurality of steps. The accommodating parts 3 are separated into first accommodating parts 10 that occupy the most of them and second accommodating parts 11 dispersed in the upper plate 2a of the tray 2 and receiving the upper step tray 2. Each second accommodating part 11 includes peripheral side plates 11a vertically extending from the peripheral edges of a bottom plate 3a, and step plates 11b extending outward from the upper ends of the peripheral side plates 11a to the upper plate 2a. When the trays 2 are stacked, the peripheral edges of the upper tray 2 are supported by the peripheral edges of the lower tray 2 such that the lower end of each second accommodating part 11 of the upper tray 2 is received and supported by the step plates 11b of the corresponding second accommodating part 11 of the lower tray 2.