A processing apparatus for substrates that include a plurality of individual substrates having a photo-curable adhesive layer interposed therebetween, including a mounting table, an irradiating device that irradiates the substrates, and a control device that controls the deflection of the substrates (X) while the individual substrates are bonded together by photo-curing the adhesive. The control device calculates a temperature difference ΔT between the temperature Th of the mounting table and the temperature Td of the substrates before curing, finds a deflection difference ΔX between the deflection X of the substrates after curing and the target deflection setting value Xt, finds a temperature Tc by calculating Tc=ΔT−M×ΔX using the constant of proportionality M; and controls the temperatures of at least one of the substrates before curing and the mounting table according to the temperature Tc such that Tc=Th−Td.