Excitons are hydrogen-like objects in solids, consisting of an electron and a hole bound together through their mutual Coulomb attraction. They play major roles in determining the optoelectronic properties of semiconductors. Magneto-optical spectroscopy provides valuable information on excitons through observation of diamagnetic shifts and Zeeman splittings, but high magnetic fields are required to observe these effects in two-dimensional semiconductors due to enhanced binding energies compared to bulk systems. We have developed a unique magnetospectroscopy setup to investigate materials in fields up to 30 T. The developed setup allows us to change the sample temperature (between 12 K and 300 K), the field direction (negative or positive), the sample configuration (Faraday or Voigt configurations), and the light source (a pulsed laser or a continuous-wave source). We first demonstrated diamagnetic shifts, Landau quantization, and superfluorescence in an InGaAs quantum well sample. Furthermore, we studied two-dimensional hybrid organic-inorganic halide perovskites, which attract much recent attention due to their promising properties for optoelectronic devices such as solar cells and light-emitting devices. We investigated their magnetooptical properties, observing unique temperature-dependent diamagnetic shifts.