1. A lifelog recording system that records, as a piece of lifelog data, life information of a user, the system comprising: a lifelog data obtaining sensor, which is configured to obtain the piece of lifelog data from an action of the user; a biometric sensor configured to obtain a biometric signal; an Electronic Control Unit (ECU) configured to estimate an emotion level, which is a quantified emotion state of the user, based on a result of monitoring the action by the user and the biometric signal; a memory device, which is configured to store the piece of lifelog data, wherein the ECU is further configured to: compute probabilities of the piece of lifelog data corresponding to each of a plurality of types of emotions, based on a feature quantity of the result of monitoring and the biometric signal, add up the probabilities of each emotion to compute an evaluation value for each emotion used in determining the user's emotion level, estimate an emotion with a highest evaluation value as the user's emotion, generate a piece of data-to-be-recorded by associating the emotion level of the user with the piece of lifelog data, determine whether the piece of data-to-be-recorded should be stored in the memory device based on the associated emotion level, and store the piece of data-to-be-recorded in the memory device if the piece of data-to-be-recorded has an emotion level in a predefined recording range.