Thermoelectric properties sensitively reflect the topology of the electronic band structure and hydrostatic pressure is the useful parameter to control the crystal structure and the corresponding electronic state.Measurements of the variation of thermoelectric properties accompanied by the topological change in the band structure could disclose the unique features of the relativistic electrons in condensed matter systems.In this review article, we describe a method for measuring the Seebeck and Nernst effect under pressure and report an actual application in the topological nodal line semimetal PbTaSe2 in which the topological band structure, nodal line (ring) structure, was changed by pressure. 3) In PbTaSe2, application of a relatively low pressure, ~ 0.3 GPa, causes a structural phase transition and annihilates 2/3 nodal rings in the momentum space. Our systematic study of pressure dependence of the Nernst coefficients reveals that magnetic field dependence of the Nernst effect dramatically change through the structural transition. We consider that Berry curvature-induced anomalous Nernst effect reduces with relative to the decrease in the number of nodal line structures. We expect that under-pressure Seebeck/Nernst measurement, which are sensitive probe to the electric structures, greatly contribute to the study of not only topological materials but also various other materials.