Is it ethical to take a leave from work to go to a job interview or should the interview be scheduled after your working hours?

There is not need to take any leave. You can easily arrange an interview through FaceTime or Skype or any other video conferencing during your lunch break time. 

i thing it will be according to your time or lets say to your job time also it depends on the  site of both jobs 

It  is not ethical to take other Interviews within your working hours. This should be conducted outside your current job. 

Of course it's best to have the interview outside the working hours, if possible and not only because of the ethics. If this is not possible, you should take a day (or at least half a day) off and solve the issue.

It is definiyely ethical to schedule the interview outside your working hours if it is OK with your potential new employer. If scheduling after your regular working hours of present job is not OK with new employer in that case preferable to take leave, one must bear in mind that your potential new employer maybe gauging you for your morals and work ethos,

from the alphabet life that the moral control our step of life..so its not ethic to think about something when am in another thing..i mean its not honesty for my present job if i think to looking for something else..if its happen by the way i well looking for it out side the time of my job 

Well....There is nothing wrong in attending an interview but it is advisable to schedule it well so that it  does not affect your current role and responsibilities.If you can manage it after your working hours that would be excellent in a way that you won't lose your day ,and if not ,there no harm in taking a day off formally and attend your interview that you think is important for your career growth.

Unless you are an axe murderer or interested in teaching ethics, not many people are going to second guess the propriety of your livelihood pursuits unless they are psychotic paranoids.  The world is a little too manic in the wrong areas sometimes.  People change positions.  

If you do not work in a place where you are comfortable enough to mention a leave request for a job interview with your employer, make an effort to take it on your lunch.  

Otherwise, take a half day off or something.