A method of manufacturing a microlens substrate having a plurality of
microlenses includes the steps of: preparing a substrate having two major
surfaces and a plurality of concave portions formed in one of the two
major surfaces, each of the concave portions having a shape corresponding
to that of each of the microlenses being formed in the one of the two
major surfaces of the substrate; preparing a base material substrate
formed of glass having a transformation point lower than that of a
constituent material constituting the substrate; and pressure-joining the
substrate to the base material substrate in a heating state. In the
pressure-joining step, the substrate is joined to the base material
substrate and the concave portions fill with the glass material of the
base material substrate which is melted by the heat.