In programming exercises,some novice learners cannot finish the work,even with unlimited time.For such learners,many debugging assist tools have been developed.However,those tools cannot resolve typical problems of the novice learners,i.e.(1)they cannot evaluate correctness of behaviors of their programs with information from the tools and(2)they don't know correct debugging process.In this paper,we propose a learning environment for debugging with "Worksheets" for learning a correct debugging process and "Synchronized observation tool" for visualizing behaviors of programs in a domain world.We carried out a preliminary experiment to evaluate learning effectiveness of our system.