法令翻訳 http://www.japaneselawtranslat...ky=&page=3

(減価償却資産の償却費の計算及びその償却の方法)
第四十九条  居住者のその年十二月三十一日において有する減価償却資産につきその償却費として第三十七条（必要経費）の規定によりその者の不動産所得の金額、事業所得の金額、山林所得の金額又は雑所得の金額の計算上必要経費に算入する金額は、その取得をした日及びその種類の区分に応じ政令で定める償却の方法の中からその者が当該資産について選定した償却の方法（償却の方法を選定しなかつた場合には、償却の方法のうち政令で定める方法）に基づき政令で定めるところにより計算した金額とする。

Calculating Depreciation Allowances for Depreciable Assets; Depreciation Methods
Article 49  The amount that, pursuant to the provisions of Article 37 (Necessary Expenses), is included in the necessary expenses that are used to calculate a Resident's real property income, business income, timber income, or miscellaneous income, as the depreciation allowance for a Depreciable Asset held by a Resident on December 31 of the relevant year is the amount calculated pursuant to Cabinet Order based on the depreciation method that the Resident has selected for Depreciable Assets from among the depreciation methods prescribed by Cabinet Order by date of acquisition and asset category (or based on the depreciation method prescribed by Cabinet Order, if the Resident does not select a depreciation method).

前項の選定をすることができる償却の方法の特例、償却の方法の選定の手続、償却費の計算の基礎となる減価償却資産の取得価額その他減価償却資産の償却に関し必要な事項は、政令で定める。

Cabinet Order establishes special provisions on the selectable depreciation methods referred to in the preceding paragraph and provides for the way of selecting a depreciation method, the acquisition costs of Depreciable Assets that is to be used as the basis of the calculation of the depreciation allowance, and other particulars that need to be prescribed concerning the depreciation of Depreciable Assets.