The dispersion characteristics of a diffractive micro-Fresnel lens (MFL) which is mass-produced for a laser diode collimator are examined for novel applications. The MFL's resolving power (Rayleigh criterion for resolution) at the design wavelength is calculated to be comparable to that of conventional dispersing prisms of the same size. A simple spectrometer with an MFL (4.5 mm diameter, 14.83 mm focal length at 0.78 μm design wavelength) and a movable pinhole (PH), is fabricated. The optimum PH diameter for both resolving power and light efficiency is 5 m, and the resolution and efficiency at the design wavelength are estimated to be 3.7 nm and 85%, respectively. The measurable spectral range determined from both the diffraction efficiency and the free spectral range of the MFL almost covers the entire visible region. The absorption spectrum of KMnO4 solution is roughly obtained using the spectrometer. The space between the MFL and the PH, and the PH's movable length, which are required for spectroscopy, are as short as 20 and 7 mm, respectively. The simple and straight-line-structured spectroscopic system utilizing a more cost-efficient MFL may lead to the realization of less expensive and compact spectrometers.