39. Are there limits on the amount a political party can spend?

Source: 
公職選挙法, 1950 (2022改正)
Public Offices Election Act, 1950 (as amended by Act No.68 of 2022)

第百九十四条　選挙運動に関する支出の金額は、公職の候補者一人につき、参議院（比例代表選出）議員の選挙にあつては政令で定める額を、その他の選挙にあつては次の各号の区分による数を当該各号の区分に応じ政令で定める金額に乗じて得た額と当該各号の区分に応じ政令で定める額とを合算した額を超えることができない。
一　衆議院（小選挙区選出）議員の選挙　その選挙の期日の公示又は告示の日において当該選挙人名簿に登録されている者の総数
二　参議院（選挙区選出）議員の選挙　通常選挙における当該選挙区内の議員の定数をもつてその選挙の期日の公示又は告示の日において当該選挙人名簿に登録されている者の総数を除して得た数

Article 194. The amount of expenditures for election campaigns shall not exceed, for each candidate for public office, the sum of the following: (i) For elections of members of the House of Councillors (elected by proportional representation), the amount specified by Cabinet Order; (ii) For other elections, the sum of the following: the amount obtained by multiplying the number specified in the following subparagraphs by the amount specified by Cabinet Order for each such subparagraph; and the amount specified by Cabinet Order for each such subparagraph.
(i) Election of a member of the House of Representatives (single-seat district election): The total number of persons registered in the relevant electoral roll on the date of the public notice or announcement of the election date.
(ii) Election of a member of the House of Councillors (electoral district election): The number obtained by dividing the total number of persons registered in the relevant electoral roll on the date of the public notice or announcement of the election date by the number of seats for members in that electoral district in a regular election.

Even though there is a limit on the amount a candidate can spend for campaigning in a given district during an election period, this campaign spending limit does not apply to a party