An automatic performance device comprising: a storage part (11b, 11c) configured to store a plurality of performance patterns; a performance part (S4, S8) configured to play a performance on the basis of one of the plurality of performance patterns stored in the storage part (11b, 11c); an input part configured to input performance information through an input device configured to receive a performance operation of a user; a selection part configured to select a performance pattern being a maximum likelihood estimation from the plurality of performance patterns stored in the storage part (11b, 11c) on the basis of the performance information input to the input part; a switching part configured to switch at least one musical expression of the performance pattern that is being played by the performance part (S4, S8) to a musical expression of the performance pattern selected by the selection part; and a likelihood calculation part (S51∼S53) configured to calculate a first likelihood for each of all or some of musical sounds included in the plurality of performance patterns stored in the storage part (11b, 11c) on the basis of the performance information input to the input part, wherein the selection part is configured to estimate one of the plurality of performance patterns stored in the storage part (11b, 11c) to be the maximum likelihood estimation on the basis of the first likelihood calculated by the likelihood calculation part (S51∼S53), the automatic performance device being characterized in further comprising an evaluation input part configured to input an evaluation of the user; and a likelihood reflection part (S20∼S23) configured to reflect the input evaluation in a second likelihood of the musical expression of the performance pattern that is being played by the performance part (S4, S8), when the evaluation has been input to the evaluation input part; and the likelihood calculation part (S51∼S53) is configured to calculate the first likelihood for each of all or some of the musical sounds included in the plurality of performance patterns stored in the storage part (11b, 11c) on the basis of the second likelihood reflected by the likelihood reflection part (S20∼S23). a storage part (11b, 11c) configured to store a plurality of performance patterns; a performance part (S4, S8) configured to play a performance on the basis of one of the plurality of performance patterns stored in the storage part (11b, 11c); an input part configured to input performance information through an input device configured to receive a performance operation of a user; a selection part configured to select a performance pattern being a maximum likelihood estimation from the plurality of performance patterns stored in the storage part (11b, 11c) on the basis of the performance information input to the input part; a switching part configured to switch at least one musical expression of the performance pattern that is being played by the performance part (S4, S8) to a musical expression of the performance pattern selected by the selection part; and a likelihood calculation part (S51∼S53) configured to calculate a first likelihood for each of all or some of musical sounds included in the plurality of performance patterns stored in the storage part (11b, 11c) on the basis of the performance information input to the input part, wherein the selection part is configured to estimate one of the plurality of performance patterns stored in the storage part (11b, 11c) to be the maximum likelihood estimation on the basis of the first likelihood calculated by the likelihood calculation part (S51∼S53), the automatic performance device being characterized in further comprising an evaluation input part configured to input an evaluation of the user; and a likelihood reflection part (S20∼S23) configured to reflect the input evaluation in a second likelihood of the musical expression of the performance pattern that is being played by the performance part (S4, S8), when the evaluation has been input to the evaluation input part; and the likelihood calculation part (S51∼S53) is configured to calculate the first likelihood for each of all or some of the musical sounds included in the plurality of performance patterns stored in the storage part (11b, 11c) on the basis of the second likelihood reflected by the likelihood reflection part (S20∼S23).