In ECS, container is actually the task wrapped by the services.
Sometime, it could be difficult to find. because when you go to the task itself the logs tab is actually the log for the task.
But in this case, I need to see the logs for the specific container that defined in the task definition.
So what do you need to do is; Go to ECS > Clusters > [your cluster] > Tasks tab > [target task] > Containers [expand the container] > Log Configuration > Log driver: awslogs > Click View logs in CloudWatch