Abstract: The apparatus for liquid-phase synthesis of isoprene from isobutylene and formaldehyde, comprising the following units of synthesis of isoprene precursors: 1,3-dioxanes synthesis unit; unit for TMC synthesis from isobutylene-containing fraction; unit for TMC synthesis from recycled concentrated isobutylene derived either from isoprene synthesis unit or from the unit for synthesis products separation and isoprene monomer isolation; isoprene synthesis unit; by-products decomposition unit; unit for synthesis products separation and isoprene monomer isolation.