Japan's Electrical Appliance and Material Safety Act (電気用品安全法, "PSE") lists 457 item categories in two groups.
- Specified electrical appliances (特定電気用品, 116 categories): higher-risk items that need conformity assessment by a registered body and carry the diamond PSE mark. DC power supply units (直流電源装置) — i.e. AC adapters — are here.
- Non-specified (特定以外, 341 categories): items where the notifying business tests against the technical standard itself and carries the round PSE mark. LED luminaires, most household appliances and lithium-ion storage batteries above 400 Wh/L per cell are here.
Why the adapter matters more than the gadget
A USB-C-powered device with no adapter in the box is often outside the list entirely. The moment you bundle a wall adapter, the adapter is a diamond item: third-party assessment, a notifying business in Japan, and marking with the importer's name. Indicative lab quotations we have collected: USD 5,000–6,500 for a diamond assessment versus USD 1,700–2,000 for a round-mark self-assessment.
The shortcut
Most brands do not certify their own adapter. They buy an adapter model that already carries the diamond PSE mark under a Japanese notifying business (many OEM adapter makers sell Japan-market versions). The obligation for the adapter then sits with that business; your remaining PSE work is whatever the main product triggers.
Two traps: the adapter's label must show the Japanese notifying business, not just "PSE" printed by a factory; and a bundled adapter changes who the specified importer is if you sell direct — see the Domestic Administrator guide.
Informational summary from public sources, not legal advice. Item lists: Cabinet Order for Enforcement of the Electrical Appliance and Material Safety Act, Appendix Tables 1 and 2 (e-Gov). Costs are indicative, from lab quotations collected September 2026.