provided is a cassette holder device in a tape recording apparatus having a body , which receives either one or more than two kinds of tape cassettes having different sizes , and loads thereof in the tape recorder body , comprising : a cassette holder member , having an insertion opening , for storing and holding therein a large size tape cassette ; and a small size tape cassette guide member disposed rotatably so that it can project into the insertion opening of the cassette holder member from above the latter , having one of side surfaces facing one of side surfaces of an inserted small size cassette with a slight gap therebetween so as to regulate and guide the position of insertion of the small size tape cassette , the one side surface of the small tape cassette guide member guiding the one side surface of the small size tape cassette so as to introduce the latter into the holder member while the guide member is rotated upward by insertion force of a large size tape cassette which is inserted into the insertion opening of the holder member and is therefore retracted outside of an insertion path of the large size tape cassette .