PURPOSE: To easily obtain at a low cost high-purity dicyclopentadiene useful as a raw material for reaction injection molding technique using a metathesis catalyst by bringing crude dicyclopentadiene into contact with a solid acid such as activated clay followed by distillation.

CONSTITUTION: Crude dicyclopentadiene is brought into contact at ca. 30°C with a solid acid (pref. activated clay) ≥0.5mmol/g and ≤0.2mmol/g in the acid points at values of Hammett acidity function (H0)of ≤+4.8 and ≤-5.5, respectively, followed by distillation, thus obtaining the objective high-purity dicyclopentadiene. When the distillation is performed, for example, in the presence of 1000ppm of an antioxidant (e.g. 2,6-di-t-butylphenol) at a reflux ratio of 2-50 under a pressure of 20mmHg in a nitrogen atmosphere using a packingtype rectification column equivalent to 20 in the number of tiers, the objective product with a purity of as high as 99% at a distillation yield of ca. 80%. Contact of the raw material with the solid acid changes the properties of polymerization inhibitory substances, leading to facilitating the distillation and purification afterwards.