A depression state determination device (1; 2; 3; 4; 5; 6), comprising: a measuring part (11; 21; 31; 41) adapted for measuring a pulsation interval of a subject, and an acceleration or an angular velocity associated with a movement of the subject (that is hereinafter referred to as an "activity"); a processing part (51; 61; 71; 101) adapted for calculating a value obtained by a procedure including a step of converting the pulsation interval to a frequency spectrum (that is hereinafter referred to as a "power spectrum") and calculating a value of definite integral of a power spectrum from frequency Lf1 to Lf2 (that is hereinafter referred to as an "LF") and a value of definite integral of a power spectrum from frequency Hfl to Hf2 (that is hereinafter referred to as an "HF"); and a determining part adapted for determining the subject to be a depression state when at least one of the following conditions [A] and [B] is satisfied: [A] In an awaking time zone of the subject, at least one of the following formulas to is calculated and satisfied: the pulsation interval × the activity < C 1 HF × the activity < C 2 LF / HF / the activity > C 3 [B] In a sleeping time zone of the subject, at least one of the following formulas to is calculated and satisfied: the pulsation interval / the activity < C 4 HF / the activity < C 5 LF / HF × the activity > C 6 wherein the Hfl > the Lf1, the Hf2 > the Lf2, and the C1 to C6 are constant number. a measuring part (11; 21; 31; 41) adapted for measuring a pulsation interval of a subject, and an acceleration or an angular velocity associated with a movement of the subject (that is hereinafter referred to as an "activity"); a processing part (51; 61; 71; 101) adapted for calculating a value obtained by a procedure including a step of converting the pulsation interval to a frequency spectrum (that is hereinafter referred to as a "power spectrum") and calculating a value of definite integral of a power spectrum from frequency Lf1 to Lf2 (that is hereinafter referred to as an "LF") and a value of definite integral of a power spectrum from frequency Hfl to Hf2 (that is hereinafter referred to as an "HF"); and a determining part adapted for determining the subject to be a depression state when at least one of the following conditions [A] and [B] is satisfied: [A] In an awaking time zone of the subject, at least one of the following formulas to is calculated and satisfied: the pulsation interval × the activity < C 1 HF × the activity < C 2 LF / HF / the activity > C 3 [B] In a sleeping time zone of the subject, at least one of the following formulas to is calculated and satisfied: the pulsation interval / the activity < C 4 HF / the activity < C 5 LF / HF × the activity > C 6 wherein the Hfl > the Lf1, the Hf2 > the Lf2, and the C1 to C6 are constant number. [A] In an awaking time zone of the subject, at least one of the following formulas to is calculated and satisfied: the pulsation interval × the activity < C 1 HF × the activity < C 2 LF / HF / the activity > C 3 [B] In a sleeping time zone of the subject, at least one of the following formulas to is calculated and satisfied: the pulsation interval / the activity < C 4 HF / the activity < C 5 LF / HF × the activity > C 6 wherein the Hfl > the Lf1, the Hf2 > the Lf2, and the C1 to C6 are constant number. <EOS>