In a cassette loading/unloading apparatus for a slot-in type cassette tape recorder using a toggle spring, a slider holds a cassette inserted therein and slides together therewith in a cassette holder. The cassette loading/unloading apparatus is provided with a spring member separate from the toggle spring. This spring member is charged with a biasing force as the slider slides at cassette insertion so that the charged biasing force may act as a resisting force on the slider. The spring member applies the resisting force to the slider before the slider passes the neutral point of the toggle spring, and is prevented from doing so after the slider passes the neutral point.