In a statement, the court said it imposed the top daily fine on Josep Maria Jove, the right-hand man of Catalan vice-president Oriol Junqueras who is one of those in charge of electoral matters in the region.
Jove was one of 14 arrested on Wednesday in a police operation targeting preparations for a referendum slated for October 1 that has been banned by Madrid and the courts.
Another official was fined 6,000 euros a day, the court said.
Both will keep receiving the fines until they can justify they have "completely paralysed any act considered as not fulfilling a suspension of the referendum," as previously dictated by the court.
The seven members of an electoral board set up for the vote were also handed a 12,000-euro daily fine and 15 people who are part of local boards were given 6,000-euro penalties.
The sanctions come on top of a host of other measures imposed by authorities to stop the referendum in a region deeply divided over independence.
Police have seized close to 10 million ballot papers destined for the vote and over 45,000 notifications due to be sent to Catalans selected to staff polling stations.
Prosecutors have threatened to arrest mayors who facilitate the vote if they do not comply with a criminal probe and Madrid has tightened control over the region's finances.
All these are making it harder and harder for Catalonia's separatist executive to stage the vote.
