To provide a user-worn device and an automatic excretion disposal apparatus for reducing the occurrence of bedsores.

Since the user-worn device is equipped with a diaper cup formed to have an approximately C-shaped cross-section for covering an abdomen to buttocks of a user, a base plate 165 arranged underneath the buttocks, a plurality of fixed bumps 161 rising on the base plate, and a plurality of variable bumps 162 which are arranged between the fixed bumps on the base plate and extend in the direction perpendicular to the base plate in a manner to exceed the height of respective fixed bumps at the time when a fluid is introduced, the load of the user's buttocks is applied to either/both the fixed protruding parts 161 or/and the variable bumps 162. Since a gap is formed between the user's buttocks and each bump, the air permeability is secured. Consequently, the occurrence of the bedsores is reduced.