We report the results of the spectrophotometric monitoring campaign of AT 2017be in NGC 2537. The light curve of AT 2017be reveals a fast rise to an optical maximum, followed by a plateau lasting about four months, and finally a fast decline. Its r-band maximum absolute magnitude is around -12.0 mag. We constrained an upper limit for the ejected Nickel mass of approximately 0.0005 solar mass. The spectra of AT 2017be show minor evolution, along with prominent H alpha, weak Fe II features, Ca II H&K and the Ca II NIR triple lines. In addition, the [Ca II] doublet is visible in all spectra. However, we did not recover a tight constraint on the progenitor of AT 2017be from HST and Spitzer. We propose that AT 2017be is a weak electron-capture supernova explosion of a super-asymptotic giant branch star, on the basis of the similarities with SN 2008S and NGC 300 OT2008-1.