The cloud computing is a computing paradigm that users can rent computing resources from service providers as much as they require. A spot instance in cloud computing helps a user to utilize resources with less expensive cost, even if it is unreliable. When a user performs tasks with unreliable spot instances, failures inevitably lead to the delay of task completion time and cause a seriously deterioration in the QoS of users. To solve the problem, we propose the VM migration scheme to reduce the job waiting time. And in this scheme we use our previously proposed checkpointing method. When a running instance occurs the out-of-bid situation (failure), the VM on the failed instance is to a new instance. Our proposed VM migration scheme reduces the rollback time and the task waiting time when an instance occur the out-of-bid situation. The simulation results show that our scheme achieves performance improvements in the task execution time of 68.94%, 68.61%, and 46.35% compared with the hour-boundary checkpointing scheme, the rising edge-driven checkpointing scheme, and our previously proposed checkpointing scheme., respectively Further, our scheme outperforms the existing schemes in terms of the reduction the total costs per spot instances for a user's bid.