Why is the devil considered evil if he keeps and put all the bad poeple in hell ?
its just a question that bothers me.

Well hes (or shes) only got 2 mentions in the bible. So dont blame the "old book" :) Its down to centuries of having a need to blame some thought form (or clever idea) for our cruel ways. Oh, and also to keep god fearing people in check.

Thats my personal view Narxes and if anyone takes offense then I offer my apologies.

Well the theoretical answer to the devil question is that not only does he do the duties of the jailer (by his own appointment and decision ) but he leads people there also and makes people stray away from God.

a method of thought that avoids blameing the "creator" for the evil that comes from his construct. the devil is an excuse.