Cleaning liquid and method for cleaning substrate

A cleaning liquid for cleaning a substrate having a first metal atom-containing layer that contains ruthenium and a second metal atom-containing layer that contains a metal atom other than ruthenium, both the layers being present in contact with each other, where at least one of the first metal atom-containing layer and the second metal atom-containing layer is exposed on a surface, the cleaning liquid comprising:

• at least one hydrazine compound (A) selected from the group consisting of a compound represented by General Formula (a1), a hydrate of the compound, and a salt of the compound;
• and
• at least one basic compound (B) which is a quaternary hydroxide,
• wherein R1 and R2 each independently represent an organic group including no carbonyl group or a hydrogen atom.