The world No.14 continued his blistering form having also landed the Swedish Open and Swiss Open earlier this month.
The Norwegian has now won each of his past 11 matches since defeat by Jordan Thompson in the opening round at Wimbledon.
Ruud, who was also a winner at the Geneva Open in May, dominated the opening set against world No.97 Martinez, who was appearing in his first ATP final.
The Spaniard defeated No.2 seed Roberto Bautista Agut on the way to reaching the showpiece, and responded well by taking a close second set.
Nevertheless, Ruud broke to take control of the decider, before closing out victory for a fourth ATP title of the season, all of which have come on clay.