In housing environment design, the theme which should be planned and designed is not given to the client and also the specialist in advance. They have to decide the frame for their collaborative practice and set up concrete and suitable subjects in the complicate and uncertain situation. Ethno-design-method is inevitably working in such situated process practically. This paper aims to describe the ethno-design-methods which are found in the relationship between "being the buyer" and "being the seller" in design action by analysis of conversations between the buyer and the seller. Housing environment design develops through the negotiation in such the relationship. The ethno-design-methods as collaborative practice were found as comprising (a) controlling information, (b) affirming by the technical knowledge and (c) keeping silent and suspending evaluation.
