In The Evil Dead series of Sam Raimi movies, the two sequels are meant to be funny. But was that the intent of the original movie?
Yes and no.
Raimi and co wanted to make a film, but felt that going for a comedy wasn't a great idea - and after doing their research at the local drive-in, knew that horror was the way to go. They made a short horror promo, Within the Woods, and the positive reaction they got from this propelled the development and shooting of Evil Dead.
Even though they were going for a full-on gross out movie, Raimi's camera techniques and love of The Stooges tinged the film - and created a horror hybrid that has influenced generations of filmmakers since.
Sam and Ted Raimi already made lots of comedies, I have a rare disc of some old short films he did before Evil Dead. It also has the Original Evil Dead on it, before it was Evil Dead, which is just twenty minutes long, I believe it was called "Within The Woods" or something like that I'm not going to check right now, but I believe that's what it's called. I have also read "If Chins Could Kill" And know Bruce Campbell's side of the story...
So, it was totally meant to be a horror movie. What happened was a local critic reviewed some of their comedy films and said that it was so ridiculous and stupid that the writers could never do anything serious, like a horror film. Sam and Ted Raimi thought they'd prove them wrong by doing the short film Within The Woods. It was meant to be scary, and when they got a lot of good reception from it, they decided to make it a full length movie and started raising money, but they tried to keep it true to the short film, which meant still scary. They WERE NOT trying to make it comedic. They were trying to stray from comedy for this one, and then they brought in the comedy for Evil Dead II.
NO, well I am not surprised by your question, it sure looks like a comedy when you watch it today but it was supposed to be a horror movie and it really was at the time. Horror movies were not as realistic in 1981 as they are now. Today horror movies do not show ghost's face directly they just create an ambiance where you would get sucked into the movie and get scared. Coming back to your question, Evil Dead 1981 was a horror movie it was the first horror movie I watched as a kid in mid 90's when I was like 5-6 (had trouble sleeping for months). The IMDB mentions only one genere for this movie and that is "Horror".