What are main differences between computer science and software engineering (e.g in demand, value, and course)? I need to do BS but I can't decide which one to choose.

I would expect no difference in demand. New hires have to learn everything, no matter the degree. Most software degrees are in CS, but that is only because SE degrees are newer. Value is your decision. If  you like theory, take CS. If you prefer software developer practices, take SE. If they had offered SE degrees when I went to school, I would have taken that instead of CS.

I am a Software Engineer and I have a BS in Computer Science. Your question is slightly ambiguous, but I will do my best. If you are trying to decide between one university offering a Software Engineering program versus a different university offering a Computer Science program, then I highly suspect that the difference is only in what each university chooses to name their curriculum.  Different schools choose different names, and curriculums may vary slighty one way or another.  If this is the case, I would suggest picking the university irrespective of the degree program's label. However, some universities may offer multiple degree programs, Computer Science, and Software Engineering.  If they do, then the difference usually comes down to some different focus in the higher level courses.  For example, a Computer Science program may require more CS theory than a Software Engineering program.  Likewise, a Software Engineering program may require more engineering courses, like Statics and/or Dynamics. If this is your case, than your best option would be to talk to the university's counselors and ask them to explain the curriculum, and the differences, to you so you can make an informed choice.  It may also be that they are similar enough that you could change your mind midway through and only have to make up a few courses.  Sometimes a CS required course may be an elective for SE, and vice versa. It most likely won't inhibit your career choices or your oppotunities.  So, my advice would be to look into whichever one interests you the most.

Check their curriculum. That's the only way you can get good answer. Even programs with the same name but in different universities can be somewhat different. In my university, there were only 3 compulsory mathematical courses. In another university which I initially wanted to go, there were 7 compulsory mathematical courses. That alone shows different mindset and culture.