The present invention provides a scroll-type expander that simultaneously performs expansion and re-heating such that efficient expansion is realized and there is no reduction in efficiency caused by pressure loss occurring during the supply of an working fluid to the scroll-type expander, and that minimizes a difference in temperature between a stationary scroll member and a rotating scroll member, as well as a temperature distribution of a scroll wrap. The present invention also relates to a heat exchange system that uses a scroll-type expander to replace pistons in a conventional reciprocating Stirling engine or refrigerator with a pair of scroll-type compressor and expander such that the heat exchange system may be used as a Stirling engine or refrigerator. The present invention also provides a steam engine, in which a steam turbine in the conventional steam engine (Rankine system) is replaced with a scroll-type expander such that the steam cycle has both a re-heating cycle and a regeneration cycle.