A high pressure fuel pump, comprising: a pressure chamber, a plunger configured to perform a reciprocating movement ascending into the pressure chamber and descending from the pressure chamber, a cylinder for guiding the reciprocating movement of the plunger, a plunger seal disposed at an end portion of the cylinder that faces away from the pressure chamber, the plunger seal being in slidable contact with an outer periphery of the plunger, a seal chamber formed between said end portion of the cylinder and the plunger seal, an intake port and a first intake passage connected to the intake port, an intake joint mounted to a pump housing of the high pressure fuel pump, a damper chamber arranged on a low-pressure fuel path extending to the pressure chamber, and a metal diaphragm damper arranged in the damper chamber, wherein the plunger has a large diameter portion and a small diameter portion, the diameter of the large diameter portion being larger than the diameter of the small diameter portion, wherein the plunger is further configured so that the large diameter portion slides in the cylinder, the small diameter portion slides in the plunger seal, and the volume of the seal chamber decreases when the plunger descends from the pressure chamber and increases when the plunger ascends into the pressure chamber, wherein the intake port is formed in the intake joint, wherein the first intake passage is connected to the damper chamber for allowing fuel flow from the first intake passage to the pressure chamber through the damper chamber, and wherein the first intake passage is also connected to the seal chamber for allowing fuel flow from the first intake passage to the seal chamber, wherein the intake joint is arranged at a lateral peripheral side of the housing and extends from the housing in a direction perpendicular to the direction of the reciprocating movement of the plunger, and wherein, along the reciprocating direction of the plunger, the intake joint is arranged between the damper chamber and the seal chamber, wherein a rate of a flow of the fuel going to the pressure chamber and a rate of flow of the fuel going to the seal chamber add up to a rate of a flow of the fuel that is guided to the first intake passage; wherein the high pressure fuel pump further comprises a second intake passage that forms part of the damper chamber and allows fuel to flow between the first intake passage and the pressure chamber, wherein the second intake passage is connected to the seal chamber via the first intake passage. a pressure chamber, a plunger configured to perform a reciprocating movement ascending into the pressure chamber and descending from the pressure chamber, a cylinder for guiding the reciprocating movement of the plunger, a plunger seal disposed at an end portion of the cylinder that faces away from the pressure chamber, the plunger seal being in slidable contact with an outer periphery of the plunger, a seal chamber formed between said end portion of the cylinder and the plunger seal, an intake port and a first intake passage connected to the intake port, an intake joint mounted to a pump housing of the high pressure fuel pump, a damper chamber arranged on a low-pressure fuel path extending to the pressure chamber, and a metal diaphragm damper arranged in the damper chamber, wherein the plunger has a large diameter portion and a small diameter portion, the diameter of the large diameter portion being larger than the diameter of the small diameter portion, wherein the plunger is further configured so that the large diameter portion slides in the cylinder, the small diameter portion slides in the plunger seal, and the volume of the seal chamber decreases when the plunger descends from the pressure chamber and increases when the plunger ascends into the pressure chamber, wherein the intake port is formed in the intake joint, wherein the first intake passage is connected to the damper chamber for allowing fuel flow from the first intake passage to the pressure chamber through the damper chamber, and wherein the first intake passage is also connected to the seal chamber for allowing fuel flow from the first intake passage to the seal chamber, wherein the intake joint is arranged at a lateral peripheral side of the housing and extends from the housing in a direction perpendicular to the direction of the reciprocating movement of the plunger, and wherein, along the reciprocating direction of the plunger, the intake joint is arranged between the damper chamber and the seal chamber, wherein a rate of a flow of the fuel going to the pressure chamber and a rate of flow of the fuel going to the seal chamber add up to a rate of a flow of the fuel that is guided to the first intake passage; wherein the high pressure fuel pump further comprises a second intake passage that forms part of the damper chamber and allows fuel to flow between the first intake passage and the pressure chamber, wherein the second intake passage is connected to the seal chamber via the first intake passage.