A separation apparatus 10 includes a pretreatment section 20 that subjects a target fluid containing an olefin compound to at least one or more of a treatment for reducing an acetylene-based compound, a treatment for reducing a sulfur compound, and a treatment for reducing a fine particle component. In the pretreatment section 20, one or more treatments selected from a hydrotreating and an adsorption treatment with an adsorbent may be performed as the treatment for reducing the acetylene-based compound, one or more treatments selected from a washing and absorption treatment, an adsorption treatment with an adsorbent, and a hydrodesulfurization treatment may be performed as the treatment for reducing the sulfur compound, and one or more treatments selected from a liquid absorption treatment, a collection treatment, or a filtration treatment with a filter may be performed as the treatment for reducing the fine particle component.