We report results of a study of doubly charmed baryons and charmed strange baryons. The analysis is performed using a 980  fb-1 data sample collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. We search for doubly charmed baryons Ξcc+(+) with the Λc+K-π+(π+) and Ξc0π+(π+) final states. No significant signal is observed. We also search for two excited charmed strange baryons, Ξc(3055)+ and Ξc(3123)+ with the Σc++(2455)K- and Σc++(2520)K- final states. The Ξc(3055)+ signal is observed with a significance of 6.6 standard deviations including systematic uncertainty, while no signature of the Ξc(3123)+ is seen. We also study properties of the Ξc(2645)+ and measure a width of 2.6±0.2(stat)±0.4(syst)  MeV/c2, which is the first significant determination.