He was born in Turin. He first trained in the Piedmont, under a painter by the name of Spirito, then was the main pupil of Pietro dal Po in Rome.
Among his patrons were Giovanni Battista Cesalassi and the Jurist Alberettti. In Naples, he painted several ceilings and frescoes, for example at the Chiesa di Santa Maria in Portico, and the cupula of Santi Apostoli. He completed an etching of a Holy Family, after Giovanni Domenico Cerrini, who was his intimate friend.
Relative to Lanfranco's style, Benaschi lightening the tints and attenuating the graphic prominence of the contours of the figures in order to achieve greater chromatic fusion and a more rough pictorialism. This style manifested in the frescoes of the chapel of Santa Maria la Nova, in the paintings of the chapel of St. Michael to the St. Apostoli, then in the fresco executed in the dome of this same church 1680, and then in the Saints on the front arches of the chapel of the church of the Gerolamini (1681).
Being ill he retired to live in the convent of Santa Maria delle Grazie in Caponapoli where he decorated the church with a vast cycle of frescoes executed with the help of Orazio Frezza and Giuseppe Castellano and depicting episodes from the Life of Christ and Virgin. During a hospitalization in that monastery, he died on the 28th of September 1688. More on Giovanni Battista Benaschi